Page 121 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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• Apocrine cells are cuboidal to columnar and exfoliate in small cohesive and uniform clusters.
• Nuclei are small, round, with finely stippled chromatin. Nucleoli are usually inconspicuous.
VetBooks.ir • The cytoplasm is scant, occasionally moderate and pale basophilic. It can contain small,
dark granules of secretory product.
• Anisokaryosis and anisocytosis are minimal and the N:C ratio is moderate to high.
• Apocrine carcinoma and apocrine duct carcinoma:
• They share similar cytological findings.
• Cellularity is variable, usually high.
• Cells are cuboidal to columnar and exfoliate in medium-large cohesive clusters. Clus-
ters may be disorganized and cells may show nuclear moulding and crowding.
• Nuclei are generally medium sized, round and with finely stippled chromatin. Nucleoli
can be variably visible, from indistinct to prominent, single or multiple.
• The cytoplasm is scant and pale to moderately basophilic and may contain dark granules.
• Anisokaryosis and anisocytosis are variable and may be marked. The N:C ratio is
moderate to high.
• Eccrine adenoma and carcinoma:
• Cytologically they mirror the apocrine adenoma and carcinoma.

Differential diagnoses
• Apocrine adenoma and duct adenoma:
• Trichoblastoma
• Basal cell tumour
• Mammary adenoma (depending on the location of the mass)
• Apocrine carcinoma and duct carcinoma:
• Mammary carcinoma (depending on the location of the mass)
• Eccrine carcinoma:
• Metastatic pulmonary carcinoma in cats (due to the location of the lesions in the footpads)

Pearls and Pitfalls
• Apocrine and duct apocrine adenomas are very similar cytologically. For this reason a
more broad diagnosis of sweat gland adenoma can be made. The distinction between
these two forms does not have any clinical implication, as they are both benign and
respond well to surgical excision.
• Both adenoma and carcinoma (secretory or ductal) can have areas of squamous differen-
tiation. This may result in the presence of anucleated squamous epithelial cells in the
aspirates, alongside the glandular epithelial cells.
• As for mammary tumours, complex and mixed adenoma and carcinoma of the sweat
glands have been described. In complex adenoma and carcinoma, alongside the epithelial
component, myoepithelial cells are observed. In mixed sweat gland adenoma and carcin-
oma, a cartilaginous and/or osseous metaplasia of the myoepithelial cells is found. These
are rare tumours in dogs and cats.