Page 126 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 5 Paraneoplastic Syndromes 105

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• Fig. 5.2 Feline thymoma-associated exfoliative dermatitis. Regional alo-
pecia involves the head, neck, and dorsal thorax with extensive scaling
and focal crusts.

Feline Paraneoplastic Alopecia
• Fig. 5.1 Diffuse nodular dermatofibrosis (ND) in a German shepherd
dog. The nodules are composed of extremely dense but well-differenti- Feline paraneoplastic alopecia has been reported in cats with pan-
ated collagen tissue (collagenous nevi) and are found predominately on creatic carcinoma and biliary carcinoma. 163,179–183 It is a non-
the limbs, although the head and trunk may be affected in advanced pruritic, symmetric, progressive alopecia affecting primarily the
cases. ventrum and medial aspect of the limbs. Hair is easily epilated,
and skin is shiny, inelastic, and thin, but not fragile. Foot pad
involvement also is common. Affected pads are painful and can be
Superficial Necrolytic Dermatitis dry, crusted, and fissured, or moist and erythematous. One study
showed that Malassezia spp. dermatitis is rare in cats, and 7 of
Superficial necrolytic dermatitis (SND) is seen most commonly in 15 affected cats had skin biopsy changes consistent with feline
dogs with hepatic disease (i.e., hepatocutaneous syndrome), 170–173 paraneoplastic alopecia, and pancreatic carcinoma was confirmed
but it also reported as a paraneoplastic syndrome in dogs and cats in 4 of these cats. 184 Given the aggressive biologic behaviors of
with glucagon-secreting tumors in the pancreas and liver. 163,171– pancreatic and biliary carcinomas, most cats presented with meta-
178 Necrolytic migratory erythema (NME) refers to the human static disease and were euthanized soon after diagnosis. However,
analog of paraneoplastic SND. in one cat with a solitary pancreatic tumor, skin changes resolved
The major dermatologic findings of SND are erosions and after surgery. 180
ulcerations, with alopecia, exudation, and adherent crusts on the
feet, pressure points (such as the elbow or hock), flank, perineal
area, muzzle, facial mucocutaneous junctions, and/or oral cavity. Feline Thymoma-Associated Exfoliative
Hyperkeratosis and fissuring of foot pads occurs in all affected Dermatitis
animals. Lesions may be painful and pruritic. Hypoaminoacide-
mia is a common feature in both paraneoplastic SND and hepa- Paraneoplastic exfoliative dermatitis has been reported in cats with
tocutaneous syndrome. 163,171–174 It has been hypothesized that thymoma. 163,185–187 It begins as nonpruritic scaling and mild ery-
the elevated glucagon levels sustain gluconeogenesis and amino thema on the head and pinnae, and then progressively involves the
acid catabolism, resulting in hypoaminoacidemia that then leads neck, trunk, and limbs (Fig. 5.2). With time, the scaling intensi-
to epidermal protein depletion and subsequent keratinocyte fies and alopecia develops. Keratosebaceous debris accumulates
necrolysis. between the digits, in the nail beds, and in the ear canals. Crusts
Resolution of SND was reported in one dog with a soli- and ulcers may develop. One reported cat also had a secondary con-
tary pancreatic glucagon secreting tumor that underwent current Malassezia spp. infection. 186 The underlying mechanism
surgery. 175 However, most dogs present with metastatic dis- is unknown, but the presence of an interface dermatitis and lym-
ease. Another dog was successfully treated with the soma- phoid cellular infiltrate on histopathology suggests a tumor-induced
tostatin analog octeotride. 176 Amino acid infusions have been immune-mediated process. 185 Most cats reported in the literature
used in people with NME and dogs with hepatocutaneous did not undergo treatment for their thymoma, but one that did
syndrome. 163,171,172 undergo surgical removal had complete resolution of skin lesions. 186