chapter 46 Tumors, Common Skin and Hair Follicle......................
DEFINITION/OVERVIEW
Skin and hair tumors are common in dogs; less common in cats.
These neoplasms involve the epidermis, dermis, hair follicles, and adnexal structures.
This chapter is intended as a list of the more frequent tumors arising from the skin
and adnexa.
ETIOLOGY/PATHOPHYSIOLOGY
Squamous cell carcinoma:
Neoplasia consisting of differentiating keratinocytes
May be well, moderately, or poorly differentiated; aggressiveness varies
Bowen’s disease (Bowenoidin situcarcinoma, multicentric SCCin situ):
More benign form
Most common in the cat; occurs in dogs as pigmented epidermal plaques
SCC “in situ” histopathology (dysplastic cells do not extend past the epi-
dermal basement membrane)
Potential viral etiology: papillomavirus (cat – FcaPV2, FcaPV3, FdPV2;
dog – novel viruses identified)
May progress to multicentric squamous cell carcinoma in situ
Solar induced:
Ultraviolet light causes mutation of tumor suppressor gene (p53); this gene
encodes a protein that prevents mutations by arresting the cell cycle when
DNA damage is detected, giving the damaged cell time to repair
Mutant form ofp53has been detected in 82% of feline pinnal SCC
SCC may also develop secondary to chronic inflammation or viral infection
Metastasis is rare; often related to tumor depth
Secondary bacterial infection results in pain and systemic symptoms. Melanocytic tumors (skin/digit):
Benign or malignant neoplasm arising from melanocytes and melanoblasts
Most melanomas arise from haired skin
Ultraviolet light exposure does not appear to play a role in the etiology
Genetic susceptibility may be a factor because breed and familial clustering is
noted
Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Dermatology, Third Edition.
Karen Helton Rhodes and Alexander H. Werner.
©2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.
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