CHAPTER 46 TUMORS, COMMON SKIN AND HAIR FOLLICLE 675
Solar induced: dogs – nasal planum, dorsal muzzle, axillae, and glabrous areas of
the ventral abdomen and medial thigh; cats – pinnal margins and nasal planum.
Melanocytic tumors:
1–7% of all skin tumors in cats
4–20% of all skin tumors in dogs
Slow or rapidly growing mass
Patient may be lame if a digit is involved.
Basal cell tumors:
15–26% of all skin tumors in the cat
6% of skin tumors in dogs.
Sebaceous gland tumors:
6–21% of skin tumors in dogs; rare in cats
Often considered incidental finding in certain breeds; cocker spaniel and poodle.
Hair follicle tumors:
Trichoepithelioma: common in dogs, uncommon in cats
Pilomatrixoma: uncommon in dogs, rare in cats
Trichoblastoma: uncommon in middle-aged dogs and cats
Tricholemmoma: rare in dogs and cats
Trichofolliculoma: rare in dogs and cats
Dilated pore of Winer: uncommon in older cats.
CLINICAL FEATURES
Squamous cell carcinoma:
Bowen’s disease:
Solitary or multiple lesions on head, digits, neck, thorax, shoulders, and
ventral abdomen
Hair associated with lesions epilates easily
Crusts cling to the epilated hair shaft
Characterized by hyperpigmented and hyperkeratotic plaques of primarily
the face, shoulders, and extremities (Figures 46.1, 46.2)
Solar induced:
Initial lesions: shallow, crusted ulcerations with peripheral alopecia and
erythema
Intermediate lesions: eroded and exudative plaques; scabbed surface
Late lesions: deep, crateriform, and indurated patches or plaques
Cutaneous horns (rare)
Locally highly invasive and destructive with significant tissue loss; neoplas-
tic tissue may extend beyond visible boundaries
Hemorrhage may be severe from erosion through local blood vessels.
Ulcerative tumors appear shallow and erosive; rapidly progress to deep
craters with tissue remodeling (Figure 46.3)
Cats: external nares may be proliferative and scabbed or ulcerative; pinnal
lesions often traumatized (Figures 46.4, 46.5)