Page 90 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Epithelial Tumours
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Key cytological features
VetBooks.ir Some cutaneous epithelial tumours can exhibit an overlap of cellular and morphological
features. In these cases, only a sub-classification is possible, leaving a list of main differential
diagnoses. Some of the cytological findings that, when present, may help in distinguishing these
cutaneous epithelial tumours from each other are as follows:

Table 8.1
Trichoblastoma (TB) versus basal cell tumour (BC):
• Ribbon-like arrangement (TB)
• Presence of pink amorphous material associated with the epithelial cells (TB)
• Stromal cells (TB)
Trichoblastoma (TB) versus trichoepithelioma (TE) and infundibular keratinizing acanthoma (IKA):
• Ribbon-like arrangement (TB)
• Presence of anucleated squamous epithelial cells (TE: large polygonal squames and/or ghost cells; IKA:
large polygonal squames)
• Neutrophilic, pyogranulomatous or granulomatous inflammation (TE and IKA)
Trichoblastoma (TB) versus sweat gland adenoma (SA):
• Ribbon-like arrangement (TB)
• Presence of pink amorphous material associated with the epithelial cells (TB)
• Tubular arrangement (rarely seen on cytology) (SA)
• Columnar epithelial cells (SA)
• Possible presence of anucleated squamous epithelial cells (SA)
• Cytoplasmic granules of secretory material (SA)
Trichoepithelioma (TE) versus infundibular keratinizing acanthoma (IKA):
• Progressive maturation of the cells from cuboidal to superficial anucleated squamous epithelial cells (IKA)
• Ghost cells (TE)
Trichoepithelioma (TE) and infundibular keratinizing acanthoma (IKA) versus pilomatricoma (PM):
• Predominance of ghost cells (PM)
• Large polytonal anucleated squamous epithelial cells (TE and IKA).

In other epithelial neoplasms, specific cytological features are present, allowing the identification
of the structure of origin and a more detailed diagnosis. For example, amongst the adnexal
epithelial tumours, sebaceous and perianal gland neoplasms are those with the more character-
istic morphological features that enable the cytologist to reach a definitive diagnosis of the
lineage of the tumour.