Page 128 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Epithelial Tumours
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VetBooks.ir Pearls and Pitfalls
Cellular atypia is often minimal giving the tumour a ‘benign’ appearance, in spite of its
•
aggressive clinical behaviour.
• In dogs, ASAC can be associated with a paraneoplastic hypercalcaemia. These patients often
develop polyuria and polydipsia.

Variants
There are multiple histological variants, which represent different degrees of differentiation of
the tumour. Common variants include the solid, rosette and tubular types. Less common are the
clear cell and signet ring variants. In a recent study, the solid growth pattern was shown to have
a significantly poorer outcome.

Differential diagnoses
• Canine clitoral carcinoma (different localization)
• Sweat gland adenoma or carcinoma arising in skin in the perineal area

Pearls and Pitfalls
A rare morphological variant (atypical or spindle cell variant) is described cytologically and
histologically. This form is characterized by a large proportion of polygonal to elongated neo-
plastic cells, occasionally forming rosette-like patterns. Nuclei are round to oval and have fine,
uniform chromatin and either a small indistinct nucleolus or no nucleolus. The cytoplasm is
moderate in amount and lightly basophilic, often with poorly defined margins. Anisokaryosis
and anisocytosis are mild.