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Article

Histopathological Study of Canine Skin Hemangiomas and Hemangiosarcomas in Uruguay

by
Belén Varela
1,*,
Camila Larrañaga
1,
Victoria Yozzi
1,
Kanji Yamasaki
1,2 and
José Manuel Verdes
1,*
1
Pathology Unit, Department of Pathobiology, Faculty of Veterinary, Universidad de la República (Udelar), Route 8 Km 18, Montevideo 13000, Uruguay
2
Japan International Cooperation Agency (JICA), Br. Artigas 417 Of. 601, Montevideo 11300, Uruguay
*
Authors to whom correspondence should be addressed.
Pets 2025, 2(4), 36; https://doi.org/10.3390/pets2040036
Submission received: 22 July 2025 / Revised: 4 October 2025 / Accepted: 9 October 2025 / Published: 15 October 2025
(This article belongs to the Special Issue Pathology in Companion Animals—From Diagnostics to Treatment)
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Abstract

We performed an histological study on all cases of canine skin hemangiomas and hemangiosarcomas that were examined between 2018 and 2020. Of the 446 dogs with skin tumors examined, 25 were diagnosed with hemangiomas and 24 were diagnosed with hemangiosarcomas. Mixed-breed dogs were the most commonly affected by both tumors. The average ages of the dogs who were diagnosed with hemangiomas and hemangiosarcomas were 8.70 and 8.36 years, respectively, with the mean age for hemangiosarcomas being slightly higher; however, this difference was not statistically significant. Both types of tumors were more common in the trunk and limbs. Sex differences in tumor frequency were not detected in dogs with hemangiomas or hemangiosarcomas. Histologically, the mixed capillary and cavernous type was the most common in cases of hemangiomas, and the mixed capillary, cavernous, and solid type and the mixed cavernous and solid type were more common in hemangiosarcoma cases compared with the other types. In addition, epithelioid hemangiosarcomas were frequently detected.

1. Introduction

Canine hemangiomas and hemangiosarcomas are tumors arising from vascular endothelial cells that occur on the skin of all body regions [1,2]. Hemangiomas can occur anywhere, at a single or multiple locations, in an animal [1,2,3]. Chronic solar damage has been suggested to be a risk factor for canine cutaneous hemangiomas [1,2,3,4]. In addition, hemangiomas present at birth or those developing during the first years of life are likely vascular malformations [3]. Similarly, some canine cutaneous hemangiosarcomas are associated with chronic solar irradiation, and dogs with short hair, light skin, or light pigmentation may be at an increased risk of developing them [1,2,4]. The most frequent primary location of canine hemangiosarcomas is reported to be the spleen [1,2,5,6,7,8,9]; however, they have also been recorded in other visceral organs such as the heart, liver, lungs, tongue, intestinal tract, and in genitalia, such as the penis [1,2,7,10,11,12,13,14,15,16,17,18]. Additionally, the skin is a common site of occurrence [1,2,3,15,16,18,19,20,21,22,23]. Morphological studies of cutaneous vascular tumors have classified hemangiomas as capillary or cavernous types based on the size of the vascular spaces and stromal quantity [3,16]. Hemangiosarcomas can be classified into two to four types (capillary, cavernous, solid, and epithelioid) based on the morphological characteristics and growth pattern of tumor cells [24,25,26,27,28,29].
We have previously reported cases of primary splenic tumors in dogs in Uruguay [30,31]. Canine hemangiomas and hemangiosarcomas are common skin tumors in Uruguay.
The aim of this study was to define the histopathological typification of skin hemangiomas and hemangiosarcomas, complementing routine hematoxylin–eosin (H&E) and Masson’s Trichrome stainings, with immunohistochemistry against von Willebrand factor (factor VIII), Cluster of Differentiation—31 (CD 31), and Cluster of Differentiation—34 (CD 34) in each type of vascular tumor, and identify some novel aspects of the morphology and population characteristics of these cancers over a 3-year period in Uruguay using surgical materials referred to the Udelar Veterinary Pathology diagnostic laboratory of Faculty of Veterinary (Udelar).

2. Materials and Methods

2.1. Dogs

This retrospective study of all skin tumors was performed between 2018 and 2020. Of these, 25 hemangiomas and 24 hemangiosarcomas were identified. The clinical information (sex, age, breed, and location) of each dog was analyzed.

2.2. Histopathology and Immunohistochemistry

Histological samples were submitted fixed in 10% formalin solution, processed, sectioned at 4 μm, stained with H&E, and examined using light microscopy (Nikon Eclipse E200®, Nikon Corporation, Tokyo, Japan). Special staining (such as Masson’s trichrome stain) was also performed to specifically stain collagen fibers in stromal connective tissue. Histopathological blinded examinations were performed using transmitted light microscopes by three different veterinary pathologists (B.V., K.Y., and J.M.V.).
In this study, we classified hemangiomas into three types as previously described: capillary, cavernous, and mixed (capillary and cavernous) [3,16]. Hemangiosarcomas were classified into the following five types as previously reported: capillary, cavernous, solid, epithelioid, and mixed (combined presence of at least two of these patterns in the same specimen) [24,25,26,28]. For immunohistochemical analysis, sections were stained with primary antibodies against CD31 (dilution 1:50, monoclonal, clone JC70A; Dako, Carpinteria, CA, USA), CD34 (dilution 1:25, monoclonal, clone ICO115; Santa Cruz, CA, USA), and factor VIII-related antigen (dilution 1:100, polyclonal, A0082 Ig fraction; Dako, Carpinteria, CA, USA) according to previously established protocols [32,33,34]. Briefly, a 3% peroxidase blocking pretreatment was performed, followed by heat-mediated antigen retrieval in a steamer (Panavox, Dongguan, China), with the slides immersed in Borg Decloaker, RTU (Biocare Medical, Pacheco, CA, USA), inside a Coplin jar for 20 min. Removing slides and rinsing in 1× phosphate-buffered saline (PBS) solution (pH 7.4) for 5 min. The primary antibody was applied to the slides, which were then left in a humid chamber at 4 °C overnight. The following morning, after rinse in PBS (pH 7.4) for 5 min, the detection system (Mouse-on-canine HRP-polymer, Biocare Medical, Pacheco, CA, USA) and Streptavidin peroxidase were applied. Staining was visualized using diaminobenzidine for 3 to 5 min, with staining progress monitored via continuous observation of the slide under a light microscope. The samples were counterstained with Mayer’s hematoxylin. Human colonic adenocarcinoma specimens were initially used as positive controls to standardize the immunohistochemical techniques. Endothelial cells from vessels in adjacent normal tissues were used as internal positive controls in all cases. Negative controls were performed for each primary antibody by replacing it with phosphate-buffered saline (PBS) solution (pH 7.4). Primary antibodies were obtained from the same clones and manufacturers as those used in previous reports [32,33,34].

2.3. Statistical Analysis

Statistical analysis was performed using PAST® version 4.03—Statistical analysis of free software for Windows, Oslo, University of Oslo, https://www.nhm.uio.no/english/research/resources/past/ (accessed on 30 October 2023). Student’s t test was used to assess the difference between the age of the groups of dogs diagnosed with hemangiomas and hemangiosarcomas. Data are presented as means ± standard deviation. The level of statistical significance used in the study was p ≤ 0.05.

3. Results

3.1. Hemangiomas

3.1.1. Dogs

Data regarding sex, age, breed, tumor location, and histological type are presented in Table 1.
Of the 446 skin tumor samples, 25 were diagnosed as hemangiomas (5.6%). Mixed-breed dogs represented the greatest proportion, followed by German Shepherds, Boxers, Cocker Spaniels, and Sharpei. Their ages ranged from 5 to 15 years (mean ± standard deviation was 8.36 ± 2.08 years); 12 were female and 13 were male. Tumors occurred most frequently in the skin of the trunk and limbs and less frequently in the skin of the head and neck.

3.1.2. Histopathology

Histologically, hemangiomas were classified as capillary (Figure 1a), cavernous (Figure 1b), or mixed based on the size of the vascular spaces and stromal quantity (Figure 1c). In the capillary type, the tumors were composed of vascular channels containing blood cells, and the blood vessel size was smaller than that in the other two types. Perivascular connective tissue was not prominent.
In the cavernous type, neoplastic blood vessels are usually separated by fibrous connective tissue, and the stroma is accompanied by lymphocytes, plasmocytes, mast cells, and macrophages, some of which contain hemosiderin debris (hemosiderophages). The presence of connective tissue and the size of blood vessels varied among individuals. The cavernous and capillary types were observed in one dog each, and the remaining 23 dogs had the mixed type.
Most tumors (24/25; 96%) were detected in the dermis, with the exception of one that originated in the subcutaneous tissue. Among those arising in the dermis, the superficial dermis was involved in the tumors in eight of the twenty-four dogs (Figure 2).
Tumor cells forming blood vessels were lined with a single layer of neoplastic cells with normochromic nuclei, and mitotic figures were rare. Thrombosis was observed in 12 cases, with some thrombi organized (Figure 3).

3.1.3. Immunohistochemistry

Immunohistochemically, almost all tumor cells were strongly positive for factor VIII-related antigen and CD31, but negative for CD34 (Figure 4). The intensity and location of the immunohistochemical labeling did not differ between the histological types of hemangiomas and hemangiosarcomas.

3.2. Hemangiosarcomas

3.2.1. Dogs

Breed, sex, tumor location, and histological type data are shown in Table 2. Of the 30 hemangiosarcomas diagnosed during the study period, 24 were skin hemangiosarcomas that were analyzed in this study. Skin hemangiosarcomas diagnosed during the study period accounted for 5.3% of all skin tumors. Hemangiosarcomas in mixed breeds represented 42% of the total study group (as expected, because the Uruguayan dog population mainly comprises crossbred dogs, and since we received more tissue specimens from mixed-breed dogs, with a small number of purebred Pitbull Terriers, Labrador Retrievers, and Boxers; mixed-breed dogs are also most frequently affected). Ages ranged from 5 to 13 years (mean ± standard deviation was 8.7 ± 2.5 years). Ten were female and fourteen were male. Tumors occurred most frequently in the trunk and limbs (50% and 34%, respectively). In addition, a tumor was observed in the lip in one case and in the scrotum in two cases.

3.2.2. Histopathology

In all of the studied cases, the information obtained from referring veterinarians or owners confirmed that there were no other pathologies associated with the hemangiosarcoma. The first author macroscopically evaluated all of the studied tumors, confirming that each was a single mass. Five of these tumors (20.8%) were present in the dermis and nineteen (79.2%) extended into the subcutaneous tissue. Ulceration due to tumor growth was observed in 17 dogs, and no capsule formation was observed in these tumors. The degree of differentiation was extremely variable, ranging from well-differentiated tumors with well-defined vascular channels to poorly differentiated tumors with minimal vascular lumen formation. The tumors were classified into capillary, cavernous, epithelioid, and solid types based on neoplastic cell differentiation (Figure 5).
Neoplastic cells often have prominent bulging nuclei that are pleomorphic and hyperchromatic with numerous mitoses. Capillary-type tumors are composed of capillary neoplastic endothelial cells that form vascular channels with variable numbers of erythrocytes. Connective tissue surrounding neoplastic vessels is not common. The cavernous type shows an atypical cavernous structure with well-differentiated spindle-shaped cells on a delicate connective tissue framework forming blood-filled cavities and channels. In addition, many cases showed irregularly shaped and sized vessels with neoplastic endothelial cell lining and trabeculae between the vascular lumens. The amount of connective tissue in the stroma varies, and lymphocytes, plasma cells, histiocytic cells, and hemosiderophages are frequently present in the stroma. In the solid type, neoplastic proliferation is composed of solid cords of immature neoplastic cells that have lost the ability to form vascular channels. Although visible vascular structures were rarely observed, some formed neoplastic blood vessels resembling an alveolar-type structure, in which the histologic features included the plump, epithelioid appearance of neoplastic endothelial cells and occasional cytoplasmic vacuolation, which rarely contained erythrocytes. The patterns of epithelioid endothelial cell growth ranged from vasoformative structures to gland/acini-like anaplastic carcinomas, and from short ducts to solid sheets. Regarding histological types, it was rare for each type described above to constitute a tumor alone. Capillary and epithelioid types were observed, whereas the other cases were mixed histological types. Nine capillary, cavernous, and solid mixed types and six cavernous and solid mixed types were observed. In addition, the epithelioid type was observed in seven mixed-type cases. Thrombi were commonly detected in all types, but were more frequent in hemangiomas.

3.2.3. Immunohistochemistry

In all types, immunohistochemistry revealed strong membranous staining for CD31 and moderately strong cytoplasmic staining for factor VIII-related antigen in neoplastic cells (Figure 6 and Figure 7). Although the controls used to standardize the immunohistochemistry technique were positive, the tumor cells and internal controls tested negative for the CD34 primary antibody used (Figure 6).

3.3. Statistical Analysis of the Age of Diagnosis of Dogs with Hemangiomas and Hemangiosarcomas

Student’s t-test did not identify any statistically significant differences in the ages of the dogs diagnosed with hemangiomas and hemangiosarcomas (Figure 8).

4. Discussion

Canine skin hemangiomas and hemangiosarcomas are commonly diagnosed in Uruguay. A survey of skin cancers diagnosed by private laboratories in Uruguay indicated 2131 diagnoses in the same period as our report, with a rate of 3% for canine skin hemangiomas and 3.3% for hemangiosarcomas. Based on this information, our results of 446 diagnosed skin tumors constitute 20.9% of the total number of diagnosed skin tumors in Uruguay during that period. In our laboratory, we diagnosed 5.6% hemangiomas and 5.3% hemangiosarcomas. Comparing our results with the information from the other private Uruguayan laboratory, we have a higher ratio for both vascular tumors (1.87:1 for hemangiomas, and 1.61:1 for hemangiosarcomas). In a recent national survey, the estimated dog population in Uruguay was 1:448.224 [35]. The complete diagnosed skin tumors from a privates and a University laboratory represent less than 0.2% of all dogs in Uruguay.
For hemangiomas, the mean age was >8 years old [3,16]. In our diagnosed hemangioma cases, the average age of the dogs at the time of excision was 8.36 ± 2.08 years; therefore, there is a difference in the average age of dogs reported in previous studies compared with our study [3]. In contrast, it has been reported that tumors had already developed at birth and during the first few years of life, suggesting a type of vascular malformation [3]. As the dogs in this study were diagnosed over 5 years old, hemangiomas due to vascular malformations were unlikely. There are contradictory reports regarding sex; some argue that there are no differences between the two sexes, whereas others propose that hemangiomas are more frequent in females than in males [3], and vice versa [16]. In our study, no sex predilection was observed. In addition, dogs with short-hair coats and lightly pigmented skin have been proposed to be more susceptible to hemangiomas and hemangiosarcomas than those with variable-length hair coats or pigmentation [3,15]. In our study, hemangiomas and hemangiosarcomas were detected in long-haired dogs of multiple breeds. Chronic solar damage has been suggested to be a cause of dermal hemangiomas [1,2,3]. Therefore, we could not establish a clear relationship between skin vascular tumors and ultraviolet light exposure. However, hemangiomas were found just below the epidermis in 8 of the 25 dogs, indicating a relationship between skin hemangiomas and solar damage, at least in these 8 cases. Further research is required to determine the relationship between dog breed and solar damage in Uruguay. The present morphological changes in hemangiomas were similar to those previously reported [3,16,36]. In this study, the formation of multiple organized thrombi was considered one of the characteristic changes. More research is required to determine the pathogeny of thrombi formation in canine cutaneous hemangiomas. The large number of organized thrombi may be related to blood flow in the tumor and the time course from tumor formation. The present study also shows that the mixed type was more common, as mentioned in the Results Section and reported previously [3]. Depending on the time from the onset of the tumor and the condition of the dog, tumors may be complicated, comprising both capillary and cavernous types, with proliferation of the connective tissue. Immunohistochemical studies have reported that factor VIII-related antigen staining is more sensitive in canine hemangiomas [37], and that CD31 markers have limited diagnostic relevance for vascular neoplasms in cats [32] but high diagnostic relevance in hemangiomas and hemangiosarcomas in dogs [38]. In our cases, the tumor cells in dogs were immunoreactive against both CD31 and factor VIII-related antigen primary antibodies, confirming their combined use as biomarkers of canine cutaneous vascular tumors.
Hemangiosarcomas are malignant neoplasms of vascular endothelial origin that easily metastasize to distant organs via hematogenous routes [1,2,4,5,14,27]. In contrast, some studies suggest that the origin of these tumor cells in cats derives from stem cells [15,39]. Although the primary site of canine hemangiosarcomas is the spleen, they have also been observed in other organs, including the heart and skin [1,2,7,10,11,12,13,14,15,16,17,18,40,41,42]. According to De Nardi et al., cutaneous hemangiosarcomas, primarily dermal, are subdivided into actinic and non-actinic hemangiosarcomas [43]. Cutaneous hemangiosarcomas are reported to account for approximately 13% of all hemangiosarcomas in dogs [15]. The frequency of cutaneous hemangiosarcomas relative to all hemangiosarcomas was 89% in the present study, and this frequency is rather high compared with previous reports of 13% in the Northern Hemisphere [15]. However, Brazilian epidemiological data have demonstrated that the incidence of canine cutaneous hemangiosarcomas could be 27–80% of all canine hemangiosarcomas in the Southern Hemisphere [43]. In addition, it has been reported that the incidence of hemangiomas is higher than that of hemangiosarcomas and that some dogs have a combination of both [3]. In our study, the frequency rate of hemangiomas was 5.6% and that of hemangiosarcomas was 5.3%; therefore, there was minimal difference in the frequency of both tumors. In addition, none of the dogs in this study had concurrent hemangiomas or hemangiosarcomas. Although it has been reported that this tumor affects breeds such as German Shepherds, Golden Retrievers, Labrador Retrievers, and Schnauzers [15], in the present study, hemangiosarcomas were not frequently observed in specific breeds. Some reports have indicated an increased prevalence in males [15,44]; however, no difference in the frequency of occurrence according to sex was observed in our study. Hemangiosarcomas are commonly found in older dogs, and the mean age of affected dogs at the time of diagnosis is 8–13 years [15,18,42,43,45,46]. The mean age of dogs with hemangiosarcomas in our study was 8.7 ± 2.5 years; however, seven out of fifteen dogs were 8 years or younger, indicating that canine skin hemangiosarcomas in Uruguay may occur more frequently in younger dogs than in older dogs. For epidemiological studies, further investigations using more materials are needed.
In the future, we intend to clarify the relationship between tumor type and clinical prognosis after tumor surgery. Therefore, in the present study, we classified hemangiosarcomas into five histological types according to tumor cell differentiation and based on previous reports [24,25,26,28]: capillary, cavernous, solid, epithelioid, and mixed types. We considered the epithelioid type to be more malignant than the other types because of the lack of tumor cell differentiation. As a result of this classification, mixed capillary, cavernous, and solid types and mixed cavernous and solid types were frequently observed. To our knowledge, the frequency of each type of hemangiosarcoma has not been well reported previously. Furthermore, we obtained interesting results regarding epithelioid cells. Epithelioid tumor cells were detected in seven mixed types, and one case of hemangiosarcoma comprising epithelioid tumor cells alone was observed. Warren and Summers reported that key histologic features in the epithelioid hemangiosarcoma were the plump, epithelioid appearance of neoplastic endothelial cells and occasional cytoplasmic vacuolation [28]. Further, Shor et al. demonstrated that a crucial characteristic finding is the discrete nests of anaplastic carcinoma-like tumor cells in epithelioid-type hemangiosarcomas [27]. Epithelioid-type hemangiosarcomas in this study showed similar histological changes to those described above, and tumor cells were positive for endothelial markers such as factor VIII-related antigen and CD31, as described by Warren and Summers [28]. According to the report of Shor et al. [27], epithelioid hemangiosarcomas that had metastasized to various organs such as the prostate, lung, liver, kidney, testis, colon, stomach, and brain were considered highly malignant. Immunohistochemistry results showed that the tumor cells of various types of hemangiomas reacted with factor VIII-related antigen and CD31. However, in our cases, the tumor cells tested negative for the CD34 mouse monoclonal primary antibody used at a dilution of 1:25 (a mouse monoclonal IgG1, previously tested in mice, rats, and humans, but with no previous and specific recommendation for use in canines), providing contradictory results with previous reports which indicate high and unspecific staining in hemangiosarcomas and in a high percentage of other nonvascular tumors. Although unlikely, another technical explanations of this result could be: (1) an inadequate antigen retrieval protocol (we used the same protocol for factor VIII and CD31); (2) an inadequate antibody dilution (we used a low dilution of 1:25); or (3) an inherent variability of CD34 expression in canine vascular tumors. This lack of specificity was proposed as a major limitation for the use of CD34 to confirm vascular tumors [1]. Factor VIII-related antigen immunopositivity has been considered a prognostic marker for hemangiosarcomas, and CD31, alone or in combination with factor VIII-related antigen, has been shown to be more specific and necessary in cases of epithelioid hemangiosarcomas [1]. In addition, there have been many reports on the usefulness of factor VIII-related antigen and CD31 in the immunohistochemical diagnosis of hemangiosarcomas, including the epithelioid type [13,14,19,21,28,32,37,47]. In this study, tumor cells positive for both antibodies were also detected in epithelioid hemangiosarcomas. Although CD34 has also been used as a marker for hemangiosarcomas, its lack of specificity limits its use for confirming vascular tumors, and the broad expression of CD34 in cat neoplasms does not warrant its use as a marker for vascular neoplasms in non-human species [1,32]. In addition, CD31 immunohistochemistry for diagnosing canine epithelioid or poorly differentiated vascular neoplasms requires attention due to potential cross-reactivity [47].

5. Conclusions

The frequency of each type of tumor in 25 skin hemangiomas and 24 hemangiosarcomas was elucidated using routine H&E and Masson’s Thricrome staining and combined immunohistochemistry against factor VIII and CD31.
CD34 is not a reliable biomarker, it was found to be non-reactive for skin vascular tumors in dogs.
Epithelioid tumor cells were detected in seven mixed types and in one case of epithelioid hemangiosarcoma, confirming a frequency of one out of three for this highly malignant type of hemangiosarcoma.
The mean age of dogs with hemangiomas at the time of excision was 8.36 ± 2.08 years, and for dogs with hemangiosarcomas, the mean age was 8.7 ± 2.5 years, this difference was not statistically significant.
No sex predilection was detected in dogs with hemangiomas or hemangiosarcomas.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/pets2040036/s1, File S1: The details of each dog’s t-test of hemangiomas and hemangiosarcomas.

Author Contributions

Conceptualization, B.V., K.Y., and J.M.V.; methodology, B.V., C.L., V.Y. and K.Y.; software, B.V., C.L. and V.Y.; validation, B.V., K.Y. and J.M.V.; formal analysis, B.V., K.Y. and J.M.V.; investigation, B.V., K.Y. and J.M.V.; resources, B.V., K.Y. and J.M.V.; data curation, B.V. and K.Y. and J.M.V.; writing—original draft preparation, B.V., K.Y. and J.M.V.; writing—review and editing, B.V., K.Y. and J.M.V.; visualization, B.V., K.Y. and J.M.V.; supervision, K.Y. and J.M.V.; project administration, K.Y. and J.M.V.; funding acquisition, K.Y. and J.M.V. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Scientific Research and Development Commission of Faculty of Veterinary-Udelar (Comisión de Investigación y Desarrollo Científico, CIDEC, FVET-Udelar, Uruguay). B.V. was an MSc fellowship recipient of Udelar’s Postgraduate Academic Commission (Comisión Académica de Posgrados, CAP-Udelar). J.M.V. is a Research Career Member of the National Research System (SNI-ANII), Uruguay, and the Program of Development of Basic Sciences (PEDECIBA), Uruguay.

Institutional Review Board Statement

Ethical review and approval were waived for this study by the Institutional Review Board CEUA-FVET-Udelar (Animal Ethics Committee of the Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay), confirming that the approval of an specific protocol is not required, since live animals were not used directly in the development of this study, due to only surgical specimens of vascular tumors of dogs were used to carried out this diagnostic investigation. The letter of exemption was received on 8 May 2025.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors would like to thank all of the owners and veterinary clinicians who referred the biopsy specimens to the Diagnostic Laboratory of the Pathology Unit, Department of Pathobiology, Faculty of Veterinary, Universidad de la República (Udelar).

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a). Hemangioma, capillary type, thin-walled capillaries (arrow) and small, irregular vascular channels (asterisk), H&E staining × 500. Scale = 50 µm. (b). Hemangioma, cavernous type, irregularly dilated vascular channels (asterisk) with walls of varying thickness lined by flat, bland endothelium (arrow), H&E staining × 500. Scale = 100 µm. (c). Hemangioma, mixed type, H&E staining × 500. Scale = 50 µm. (d). Hemangioma, capillary type, thin-walled capillaries (arrow) and small, irregular vascular channels (asterisk), Masson’s Trichrome staining × 500. Scale = 50 µm. (e). Hemangioma, cavernous type, irregularly dilated vascular channels (asterisk) with walls of varying thickness lined by flat, bland endothelium (arrow), Masson’s Trichrome staining × 500. Scale = 100 µm. (f). Hemangioma, mixed type, Masson’s Trichrome staining × 500. Scale = 50 µm.
Figure 1. (a). Hemangioma, capillary type, thin-walled capillaries (arrow) and small, irregular vascular channels (asterisk), H&E staining × 500. Scale = 50 µm. (b). Hemangioma, cavernous type, irregularly dilated vascular channels (asterisk) with walls of varying thickness lined by flat, bland endothelium (arrow), H&E staining × 500. Scale = 100 µm. (c). Hemangioma, mixed type, H&E staining × 500. Scale = 50 µm. (d). Hemangioma, capillary type, thin-walled capillaries (arrow) and small, irregular vascular channels (asterisk), Masson’s Trichrome staining × 500. Scale = 50 µm. (e). Hemangioma, cavernous type, irregularly dilated vascular channels (asterisk) with walls of varying thickness lined by flat, bland endothelium (arrow), Masson’s Trichrome staining × 500. Scale = 100 µm. (f). Hemangioma, mixed type, Masson’s Trichrome staining × 500. Scale = 50 µm.
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Figure 2. Epidermal hemangioma, mixed type. Two areas are represented, a central one composed of small vessels and poor collagenous content (arrowhead) and a peripheral one with large vessels and a greater amount of connective tissue (arrow), H&E staining × 40. Scale = 300 µm.
Figure 2. Epidermal hemangioma, mixed type. Two areas are represented, a central one composed of small vessels and poor collagenous content (arrowhead) and a peripheral one with large vessels and a greater amount of connective tissue (arrow), H&E staining × 40. Scale = 300 µm.
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Figure 3. Organized thrombi in mixed cutaneous hemangioma (asterisk). H&E ×100. Scale = 100 µm.
Figure 3. Organized thrombi in mixed cutaneous hemangioma (asterisk). H&E ×100. Scale = 100 µm.
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Figure 4. (a). Hemangioma, capillary type, strong cytoplasmatic positivity for factor VIII-related antigen (arrow) × 500. Scale = 50 µm. (b). Hemangioma, cavernous type, strong cytoplasmatic positivity for factor VIII-related antigen (arrow) × 500. Scale = 100 µm. (c). Hemangioma, mixed type, strong cytoplasmic positivity for factor VIII-related antigen (arrow) × 500. Scale = 50 µm. (d). Hemangioma, capillary type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (e). Hemangioma, cavernous type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (f). Hemangioma, mixed type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (g). Hemangioma, capillary type, negativity for factor CD34 antigen × 500. Scale = 100 µm. (h). Hemangioma, cavernous type, negativity for factor CD34 antigen × 500. Scale = 100 µm. (i). Hemangioma, mixed type, negativity for factor CD34 antigen × 500. Scale = 100 µm.
Figure 4. (a). Hemangioma, capillary type, strong cytoplasmatic positivity for factor VIII-related antigen (arrow) × 500. Scale = 50 µm. (b). Hemangioma, cavernous type, strong cytoplasmatic positivity for factor VIII-related antigen (arrow) × 500. Scale = 100 µm. (c). Hemangioma, mixed type, strong cytoplasmic positivity for factor VIII-related antigen (arrow) × 500. Scale = 50 µm. (d). Hemangioma, capillary type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (e). Hemangioma, cavernous type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (f). Hemangioma, mixed type, strong membranous positivity for factor CD31 antigen (arrow) × 500. Scale = 100 µm. (g). Hemangioma, capillary type, negativity for factor CD34 antigen × 500. Scale = 100 µm. (h). Hemangioma, cavernous type, negativity for factor CD34 antigen × 500. Scale = 100 µm. (i). Hemangioma, mixed type, negativity for factor CD34 antigen × 500. Scale = 100 µm.
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Figure 5. (a). Hemangiosarcoma, capillary type, H&E staining × 500. Scale = 50 µm. (b). Hemangiosarcoma, cavernous type, H&E staining × 500. Scale = 50 µm. (c). Hemangiosarcoma, epithelioid type, polygonal endothelial cells line vascular channels (arrowheads), H&E staining × 500. Scale = 50 µm. (d). Hemangiosarcoma, solid type (asterisk), H&E staining × 500. Scale = 50 µm. (e). Hemangiosarcoma, capillary type, Masson’s Trichrome staining × 500. Scale = 50 µm. (f). Hemangiosarcoma, cavernous type, Masson’s Trichrome staining × 500. Scale = 50 µm. (g). Hemangiosarcoma, epithelioid type, polygonal endothelial cells line vascular channels (arrowheads), Masson’s Trichrome staining × 500. Scale = 50 µm. (h). Hemangiosarcoma, solid type (asterisk), Masson’s Trichrome staining × 500. Scale = 70 µm.
Figure 5. (a). Hemangiosarcoma, capillary type, H&E staining × 500. Scale = 50 µm. (b). Hemangiosarcoma, cavernous type, H&E staining × 500. Scale = 50 µm. (c). Hemangiosarcoma, epithelioid type, polygonal endothelial cells line vascular channels (arrowheads), H&E staining × 500. Scale = 50 µm. (d). Hemangiosarcoma, solid type (asterisk), H&E staining × 500. Scale = 50 µm. (e). Hemangiosarcoma, capillary type, Masson’s Trichrome staining × 500. Scale = 50 µm. (f). Hemangiosarcoma, cavernous type, Masson’s Trichrome staining × 500. Scale = 50 µm. (g). Hemangiosarcoma, epithelioid type, polygonal endothelial cells line vascular channels (arrowheads), Masson’s Trichrome staining × 500. Scale = 50 µm. (h). Hemangiosarcoma, solid type (asterisk), Masson’s Trichrome staining × 500. Scale = 70 µm.
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Figure 6. (a). Hemangiosarcoma, capillary type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 70 µm. (b). Hemangiosarcoma, cavernous type, strong cytoplasmatic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (c). Hemangiosarcoma, epithelioid type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (d). Hemangiosarcoma, solid type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (e). Hemangiosarcoma, capillary type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (f). Hemangiosarcoma, cavernous type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (g). Hemangiosarcoma, epithelioid type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (h). Hemangiosarcoma, solid type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (i). Hemangiosarcoma, capillary type, negativity for factor CD34 antigen × 500. Scale = 50 µm. (j). Hemangiosarcoma, cavernous type negativity for factor CD34 antigen × 500. Scale = 50 µm. (k). Hemangiosarcoma, epithelioid type negativity for factor CD34 antigen × 50. Scale = 50 µm. (l). Hemangiosarcoma, solid type negativity for factor CD34 antigen × 500. Scale = 50 µm.
Figure 6. (a). Hemangiosarcoma, capillary type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 70 µm. (b). Hemangiosarcoma, cavernous type, strong cytoplasmatic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (c). Hemangiosarcoma, epithelioid type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (d). Hemangiosarcoma, solid type, strong cytoplasmic positivity for factor VIII-related antigen × 500. Scale = 50 µm. (e). Hemangiosarcoma, capillary type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (f). Hemangiosarcoma, cavernous type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (g). Hemangiosarcoma, epithelioid type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (h). Hemangiosarcoma, solid type, strong membranous positivity for factor CD31 antigen × 500. Scale = 50 µm. (i). Hemangiosarcoma, capillary type, negativity for factor CD34 antigen × 500. Scale = 50 µm. (j). Hemangiosarcoma, cavernous type negativity for factor CD34 antigen × 500. Scale = 50 µm. (k). Hemangiosarcoma, epithelioid type negativity for factor CD34 antigen × 50. Scale = 50 µm. (l). Hemangiosarcoma, solid type negativity for factor CD34 antigen × 500. Scale = 50 µm.
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Figure 7. Cutaneous hemangiosarcoma, mixed type composed of the capillary type at the left side (arrow) and solid and epithelioid types at the right side of the same figure (asterisk). H&E × 40. Upper inset: Strong cytoplasmatic positivity for factor VIII-related antigen × 400. Lower inset: Strong membranous positivity for CD31 × 400. Scale = 100 µm.
Figure 7. Cutaneous hemangiosarcoma, mixed type composed of the capillary type at the left side (arrow) and solid and epithelioid types at the right side of the same figure (asterisk). H&E × 40. Upper inset: Strong cytoplasmatic positivity for factor VIII-related antigen × 400. Lower inset: Strong membranous positivity for CD31 × 400. Scale = 100 µm.
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Figure 8. Comparison of the mean ages of diagnosis of dogs with hemangiomas (HA, n = 25, mean ± standard deviation = 8.36 ± 2.08 years) and hemangiosarcomas (HAS, n = 24, mean ± standard deviation = 8.7 ± 2.5 years). Boxes represent interquartile ranges, and lines across boxes the median values. No statistically significant differences between groups of dogs with hemangiomas and with hemangiosarcomas were detected using Student’s t test (p = 0.597)—for details of each dog, see the Supplementary Materials.
Figure 8. Comparison of the mean ages of diagnosis of dogs with hemangiomas (HA, n = 25, mean ± standard deviation = 8.36 ± 2.08 years) and hemangiosarcomas (HAS, n = 24, mean ± standard deviation = 8.7 ± 2.5 years). Boxes represent interquartile ranges, and lines across boxes the median values. No statistically significant differences between groups of dogs with hemangiomas and with hemangiosarcomas were detected using Student’s t test (p = 0.597)—for details of each dog, see the Supplementary Materials.
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Table 1. Clinical and histological data of hemangiomas.
Table 1. Clinical and histological data of hemangiomas.
ItemsDogs (%)
Breeds (n = 25)
Mixed11 (44)
German Shepherd3 (12)
Boxer2 (8)
Cocker Spaniel2 (8)
Sharpei2 (8)
Others5 (20)
Sex (n = 25)
Male13 (52)
Female12 (48)
Localization (n = 25)
Limbs10 (40)
Trunk9 (36)
Neck3 (12)
No information3 (12)
Histological occurrence site (n = 25)
Dermis24 (96)
Subcutaneous tissue1 (4)
Histological types (n = 25)
Mixed capillary and cavernous types23 (92)
Capillary type1 (4)
Cavernous type1 (4)
Table 2. Clinical and histological data of hemangiosarcomas.
Table 2. Clinical and histological data of hemangiosarcomas.
ItemsDogs (%)
Breeds (n = 24)
Mixed10 (42)
Pitbull Terrier3 (13)
Labrador Retriever2 (8)
Boxer2 (8)
Others7 (29)
Sex (n = 24)
Male10 (42)
Female14 (58)
Localization (n = 24)
Trunk12 (50)
Limbs8 (34)
Scrotum2 (8)
Lip1 (4)
No information1 (4)
Histological types (n = 24)
Mixed capillary, cavernous, and solid types9 (39)
Mixed cavernous and solid types6 (25)
Mixed capillary, cavernous, solid, and epithelioid types2 (8)
Mixed solid and epithelioid types2 (8)
Mixed capillary, solid, and epithelioid types2 (8)
Mixed cavernous, solid, and epithelioid types1 (4)
Capillary type1 (4)
Epithelioid type1 (4)
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Varela, B.; Larrañaga, C.; Yozzi, V.; Yamasaki, K.; Verdes, J.M. Histopathological Study of Canine Skin Hemangiomas and Hemangiosarcomas in Uruguay. Pets 2025, 2, 36. https://doi.org/10.3390/pets2040036

AMA Style

Varela B, Larrañaga C, Yozzi V, Yamasaki K, Verdes JM. Histopathological Study of Canine Skin Hemangiomas and Hemangiosarcomas in Uruguay. Pets. 2025; 2(4):36. https://doi.org/10.3390/pets2040036

Chicago/Turabian Style

Varela, Belén, Camila Larrañaga, Victoria Yozzi, Kanji Yamasaki, and José Manuel Verdes. 2025. "Histopathological Study of Canine Skin Hemangiomas and Hemangiosarcomas in Uruguay" Pets 2, no. 4: 36. https://doi.org/10.3390/pets2040036

APA Style

Varela, B., Larrañaga, C., Yozzi, V., Yamasaki, K., & Verdes, J. M. (2025). Histopathological Study of Canine Skin Hemangiomas and Hemangiosarcomas in Uruguay. Pets, 2(4), 36. https://doi.org/10.3390/pets2040036

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