Page 181 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

VetBooks.ir 10 Round Cell Tumours

Neoplasms included in this group originate from different cell lines, but have been historically
grouped all together as they share similar cytological features. Round cell tumours include:
• Mast cell tumour (MCT).
• Cutaneous histiocytoma.
• Plasma cell tumour.
• Transmissible venereal tumour (TVT).
• Cutaneous lymphoma.
Cytological diagnosis of cutaneous round cell tumours

Aspiration from round cell tumours usually harvests high numbers of cells. These cells are
discrete, round to oval shaped, hence the name. Although round cells do not cluster together or
produce extracellular matrix, in very thick and hypercellular aspirates they may give the impres-
sion of forming organized structures. In this case, it is important to look at their arrangement in
the thinnest areas of the slides.
Each of the round cell tumours listed above has additional specific morphological features
that facilitate their recognition on cytology. The ability to differentiate cytologically different
round cell tumours is clinically important, as the biological behaviour of these neoplasms and
the therapeutic options differ significantly. As an example, cutaneous histiocytoma often
undergoes spontaneous regression, whereas mast cell tumour is generally approached with wide
surgical excision and may have malignant potential. The morphology of these tumours will be
described in detail in this chapter.

168 © Francesco Cian and Paola Monti 2019. Differential Diagnosis in Small Animal Cytology
(F. Cian and P. Monti)