Page 195 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Chapt er 10
182

Differential diagnoses
VetBooks.ir • Lymphoma
Cutaneous histiocytoma (in dogs)
•
• Peripheral nerve sheath tumour (in cats)
• Amelanotic melanoma (when poorly differentiated/granulated)
• Extraskeletal osteosarcoma

Pearls and Pitfalls
• Morphological features are not predictive of the biological behaviour and also markedly
pleomorphic plasma cell tumours have a benign behaviour. However, the more atypia is
present, the more difficult it is to differentiate this tumour from other neoplasms. In
these cases, immunocyto/histochemical studies may help in reaching a definitive diagnosis.
Plasma cells are often positive to MUM1 and, in a variable percentage of cases, to other
B-cell markers (e.g. CD79a, CD20).
• When in doubt between plasma cell tumour and histiocytoma, the presence of promin-
ent anisokaryosis and multinucleation is considered more supportive of plasma cell
tumour.

Fig. 10.12. Dog. Plasma cell tumour. Wright-Giemsa.