Case 170526-1

The subject was a 3.5-year-old, male, castrated, Doberman pinscher.

This dog was presented to a dermatology service for evaluation of marked pruritus and crusting lesions. These lesions were first noted four months prior to presentation, and they eventually developed into progressive pruritic and crusting lesions associated with the nose and all four feet. Several antibiotic treatments did not improve the dogs clinical condition but he did seem to improve on prednisone. A diagnosis of superficial necrolytic dermatitis (SND) was made from skin biopsies. Within days the patient was readmitted to the emergency service due to rapid deterioration in quality of life. Euthanasia was elected

The pads of all four feet were moderately to severely thickened by crusts with multifocal deep fissures. The pads were reddened with multifocal, erosions and ulcers. The skin between the paw pads of the distal limbs, as well as the skin on the elbows and hocks, was similarly thickened and had fissures and crusts. The skin associated with the left hip, the right stifle, and the sternum, had a mild to moderate amount of flaking. Multifocal to coalescing thick, tan-brown crusts extended proximally along the muzzle. The entire nasal planum had mild crusts. There was mild periocular alopecia with mild, crusting of the periocular skin and mild, crusting at the commissures of the lips.

The superficial cervical lymph nodes were firm and were enlarged up to 4.5 x 2.5 x 1 cm. They bulged slightly on cut surfaces and were mottled light tan to tan. A cluster of three to five lymph nodes at the mesenteric root were firm and the largest was 1.5 x 1 x 0.5 cm. On cut surface the parenchyma slightly bulged and has multifocal to coalescing very firm, light tan regions.

A focal, discrete, spherical, approximately 1- to 2-mm-diameter, pale-tan, firm nodule was identified on cut sections of the pancreas.

This slide has a single section of tissue which is surrounded by a thin fibrous capsule and is almost completely effaced by a multinodular mass. A few small clusters of peripheralized lymphocytes remain, suggestive of remnant lymph node. The mass is composed of cords and nests of proliferative cells supported by a moderate amount of fibrovascular trabecular stroma. Neoplastic cells are cuboidal to polygonal, with small to moderate amounts of eosinophilic, occasionally vacuolated cytoplasm and a round nucleus with hyperchromatic or coarsely stippled chromatin. In some areas the nuclei are basilar and palisade against the surrounding stroma. Anisocytosis and anisokaryosis are mild, and no mitotic figures are seen. Thin cords and nests of the atypical cells infiltrate the fibrous trabeculae and, to a lesser degree, the surrounding capsule, with occasional extension beyond the external capsule. There is also multifocal to coalescing aggregates of lymphocytes and plasma cells in the fat around the capsule.

Immunohistochemistry was not performed on the lymph node mass. However, a nodule in the pancreas had the same microscopic appearance and the cells of the mass had moderate but generalized, cytoplasmic immunoreactivity for glucagon.

Mesenteric lymph node: Metastatic glucagonoma

The mass that effaced the lymph node was considered to be a metastasis from a small glucagonoma identified in the pancreas. Lesions in multiple sections of affected skin were consistent with SND, as diagnosed from the biopsy samples. Although glucagonomas have been associated with SND it is more typically related to severe, idiopathic or drug-induced vacuolar hepatopathy, the hepatocutaneous syndrome. Other neuroendocrine neoplasms (e.g. insulinomas) have occasionally been associated with SND. Although insulinomas are more common in dogs, it seems that SND is more frequently associated with glucagonomas (alpha-cell adenomas).

Although the pathogenesis of SND is not well understood, the lesions are consistent among cases and can be very striking. Typically, affected dogs have bilaterally symmetrical hyperkeratosis with crusts and skin fissures on the muzzle, lips, periocular skin, flanks, perineum, feet and pressure points, such as the elbows and hocks. The oral mucosa can also be affected. Histologically, the skin has parakeratotic hyperkeratosis with serocellular crusts. The epidermis is affected by intracellular edema and necrosis of keratinocytes. The basal cells are hyperplastic. The three changes together result in layers of red, white and blue, reminiscent of the French flag.

In some cases, the epidermal edema may be less apparent. Other parakeratotic skin diseases would have to be considered as differential diagnoses. These would include zinc-responsive hyperkeratosis, lethal acrodermatitis of bull terriers and thallium toxicity.

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