Page 101 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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• Solid/cystic variant:
• Reported rarely in dogs.
VetBooks.ir • Masses are often multilobular. Lobules can have a central cyst delineated by small kera-
tinocytes. Cysts contain pale basophilic proteinaceous material or black necrotic material.
• Melanocytes may be present amongst the epithelial cells.
• Trabecular variant:
• Multilobulated tumour, common in cats and rare in dogs.
• Cells at the periphery of the tumour are in palisades and cuboidal. Cells in the centre of
the neoplasm have slightly more cytoplasm.
• Melanocytes can be found amongst the neoplastic cells, singly or in small groups.
• Spindle cell variant:
• This variant is more common in cats and rare in dogs.
• Cells are uniform, elongated and occur individually and in variably sized cohesive clus-
ters.
• Nuclei are small and cigar-shaped, with coarse chromatin and 1–2 small prominent
nucleoli.
• The cytoplasm is pale basophilic, elongated and with inconspicuous cell margins.

Differential diagnoses
• Basal cell tumour (cats)
• Sweat gland adenoma
• Sebaceous epithelioma (though sebocytes are usually seen)
• Melanocytoma (when trichoblastoma is heavily pigmented)
• Granular cell tumour (for the granular cell variant. However, granular cell tumour in skin
is very rare in dogs and cats)

Fig. 8.8. Dog. Trichoblastoma. Uniform cuboidal epithelial cells. They show the typical arrangement in palisades.
Cells are associated with a small amount of pink amorphous material (basement membrane). Wright-Giemsa.