Page 113 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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8.4 Sebaceous Tumours
VetBooks.ir Sebaceous adenoma, epithelioma and carcinoma

Tumours that arise from the sebaceous epithelial cells in the dermis.

Clinical features

• Sebaceous adenoma:
• Common benign tumour of dogs and rare in cats, except for Persian cats.
• Age in dogs: 8–13 years old.
• Lesions are usually solitary, often exophytic (pedunculated). They can be alopecic,
hyperpigmented and ulcerated.
• In dogs, it more frequently occurs on the head.
• In cats, it arises most commonly on the head, tail and back.
• Over-represented canine breeds: Cocker Spaniel, Siberian Husky.
• Sebaceous epithelioma:
• Common tumour in dogs and rare in cats.
• Age in dogs: 10–15 years old.
• It most commonly arises on the head.
• It can appear macroscopically dark/black, as the tumour may contain melanocytes.
• Over-represented canine breeds: Irish Water Spaniel, Cocker Spaniel, German
Wirehaired Pointer and Canadian Eskimo Dog.
• Sebaceous carcinoma:
• Rare tumour in both dogs and cats.
• Age: 10–13 years old in dogs; 8–15 years old in cats.
• Lesions are usually solitary, multilobulated, often alopecic and ulcerated.
• In dogs, it more frequently occurs on the head and neck.
• In cats, it more commonly arises on the head, thorax and perineum.
• Metastasis to the draining lymph nodes can occur.
• Over-represented canine breeds: Cavalier King Charles Spaniel, Cocker Spaniel,
Siberian Husky, Samoyed and West Highland White Terrier.

Cytological features
• Cellularity is variable, generally moderate.
• Background: clear or pale basophilic. It occasionally contains a variable amount of negatively
staining amorphous material (sebum).
• Sebaceous adenoma:
• The tumour is composed of a predominance of sebocytes with low numbers of reserve
cells and ducts.
• Sebocytes are well differentiated and arranged in variably sized, often tridimensional
clusters.
• Nuclei are small, dense and central.
• The cytoplasm is abundant and heavily vacuolated. It contains numerous small, clear,
punctate vacuoles.
• Anisokaryosis and anisocytosis are minimal. The N:C ratio is low.
• Low numbers of reserve epithelial cells may be seen (less than 50% of the cells). These
are uniform cuboidal epithelial cells with small round nuclei and scant cytoplasm.