*Article* **Pleural Solitary Fibrous Tumors—A Retrospective Study on 45 Patients**

**Cornel Savu 1,2,\*, Alexandru Melinte 1, Radu Posea 1, Niculae Galie 1,2, Irina Balescu 3, Camelia Diaconu 4,5 Dragos Cretoiu 6,7, Simona Dima 8, Alexandru Filipescu 9,10, Cristian Balalau 11,12 and Nicolae Bacalbasa 8,9,13**


Received: 4 March 2020; Accepted: 14 April 2020; Published: 16 April 2020

**Abstract:** *Introduction:* The purpose of this paper is to study the type, the clinical presentation, and the best diagnostic methods for pleural solitary fibrous tumors (PSFTs), as well as to evaluate which is the most appropriate treatment, especially as PSFTs represent a rare occurrence in the thoracic pathology. *Material and Method:* A retrospective study was conducted on a group of 45 patients submitted to surgery between January 2015 and December 2019. In most cases, the diagnosis was established through imaging studies—thoracic computed tomography (CT) scan with or without contrast—but also using magnetic resonance imaging (MRI) or positron emission tomography (PET) scans when data from CT scans were scarce. All patients were submitted to surgery with curative intent. *Results*: Most patients included in this study were asymptomatic, with this pathology being more common in patients over 60 years of age, and more common in women. The occurrence of malignant PSFT in our study was 17.77% (8 cases). All cases were submitted to surgery with curative intent, with a single case developing further recurrence. In order to achieve complete resection en bloc resection of the tumor with the chest wall, resection was performed in two cases, while lower lobectomy, pneumectomy, and hemidiaphragm resection, respectively, were needed in each case. Postoperative mortality was null. *Conclusion*: Thoracic CT scan remains the most important imagistic investigation in diagnosing. MRI is superior to thoracic CT, especially in cases that involved the larger blood vessels within the thorax, spinal column, or diaphragm. Complete surgical resection is the gold standard in treatment of PSFT, and the prognosis in benign cases is very good.

**Keywords:** PSFT; resection; surgery

#### **1. Introduction**

Pleural solitary fibrous tumors (PSFTs) are rare tumors, and their evolution is considered unpredictable. The incidence of this disease is considered to be lower than 5% of the total number of pleural tumors [1]. The first case of PSFT was described from a histological view by Wagner in 1870 [2], however, the first pleural tumor was presented by Lieutaud in 1767 [3,4]. In 1931, Klemperer and Rabin published a histopathological description and divided the tumors in two categories: diffuse and localised [5]. Stout and Murray (1942) were the first to identify the mesenchymal origin of pleural tumors, which was later confirmed by electronic microscopy and immunohistochemistry [6]. Over time, these tumors have had different names: localised mesothelioma, benign mesothelioma, fibrous mesothelioma, pleural fibroma, benign pleural fibroma, pleural fibromyxoma, localised fibrous tumor, and so on [7].

Over the last 20 years, the term mesothelioma was replaced by solitary fibrous pleural tumor. These tumors were first described as being within the pleura, but it was later observed that it can also have an extra pleural localisation. There were also cases described of fibrous solitary tumors in various locations: liver, pelvis, peritoneum, meningeal, adrenal gland, intrapulmonary, urinary bladder, pericardium, and almost every organ system [8,9].

PSFTs are found within the pleura in 57.7% of cases, with the rest (42.3%) being localized extrapleural [8,10]. The World Health Organization (2015) reviewed the classification of pleural tumors from a pathological view and placed them in three categories: mesothelial tumors, mesenchymal tumors, and lympho-proliferative disorder. Both benign and malignant solitary fibrous tumors are part of the mesenchymal tumor group, along with desmoid tumors and calcified fibrous tumors.

#### **2. Materials and Methods**

This paper represents a retrospective study on a series of 45 patients diagnosed with PSFT who were submitted to surgery in our thoracic surgery clinic from the Institute of Pneumology, Bucharest over a period of five years (2015–2019). After obtaining the approval of the Ethical Committee no 12/9 February 2020, data of these patients were retrospectively reviewed. The analyzed parameters were represented by age, sex, clinical presentation, blood test results, imaging aspects, histopathological examination of the tumor after surgery, type of surgical resection, complementary treatment, and postoperative evolution. For a better classification of our series, we used the tumor size criteria (larger or smaller than 10 cm), with the De Perrot staging of pleural fibrous tumors (Table 1).


**Table 1.** Pleural solitary fibrous tumor (PSFT) staging De Perrot.

Differentiation between malignant and benign PSFT was done using the criteria established by England et al. [11]: presence of tumoral necrosis; presence of atypical nuclei, cellular pleomorphism, and hypercellularity; presence ≥4 mitosis/10 HPF (high power field). Immunohistochemistry tests were performed for both types of PSFTs.

Imaging studies consisted of chest X-ray, thoracic computed tomography (CT) scan, magnetic resonance imaging (MRI), and positron emission tomography (PET) scan. Both CT guided biopsy as well as direct tumor biopsy were used for histological diagnosis. Bronchoscopy was used in larger tumors with compression of the lung with a visible impact on the bronchial tree. Other routine tests performed were electrocardiography (EKG), lung function tests, blood gas levels, and transthoracic echography associated with a cardiology exam. Patients were also classified according to their smoking status as well as according to their exposure to asbestos or ionizing radiation.

Follow-up was done with the following protocol: standard chest X-ray at three and six months postoperative, thoracic CT scan every six months in the first two years and once a year for the next five years. Most patients from our series are still in the postoperative follow-up program, as we have set a 15 year monitoring period.
