*2.2. B. Types of Cells Involved*

Different types of cells are considered in the diagnosis of nasal diseases. Considering the diversity of the cells present in the nasal mucosa, it is, therefore, appropriate to draw up a classification of the different cytotypes present both in a healthy individual and in an individual with a pathology. The nasal mucosa cells belonging to a cytotype show some elements with high similarity; however, each cytotype appears quite different from all the others. These features allow their automatic classification [23]. A brief description of the appearance of each of the cells located in the nasal mucosa is reported below, and corresponding sample images are shown in Figure 1:

Ciliated: Among the most common cytotypes of the nasal mucosa are ciliated cells. They have a polygonal shape and a nucleus situated at various heights from the basement membrane. The apical region, the seat of the ciliary apparatus, is recognized as a well-represented body that includes a large part of the cytoplasm and the nucleus;

Muciparous (goblet cells): The muciparous cell is in the shape of a cup and is a unicellular gland. The nucleus is always situated in the basal position (the strengthener of the nuclear chromatin is typical) while the vacuoles, containing mucinous granules, are located above the nucleus, giving the mature cell its characteristic chalice shape;

Neutrophil: characterized by a polylobate nucleus, whose lobes are joined by very thin strands of nuclear material within the cytoplasm, which contains finely colored granules;

Eosinophil: usually has a bilobed nucleus and acidophilous granules that intensely stain with eosin (hence the name) as an orange-red color;

Mast cell: a granulocyte with an oval nucleus, covered in purple.

The nasal mucosa of a healthy individual normally contains ciliated, mucipara, striated, basal, and sporadic neutrophils cells. In the nasal epithelium, there can also be different types of inflammatory cells, where each of them can be a sign of a nasal pathology. They are known as immunophlogosis cells (eosinophils, mast cell, lymphocyte). Additionally, a significant presence of neutrophils is interesting—knowing the functions they perform helps motivate different therapeutic strategies [37]. Here, metaplastic cells have been merged into one class (epithelial) with ciliated cells because their nuclei are similar and this merging does not influence the diagnostic protocol.
