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In humans, cutaneous metastasis of transitional cell carcinoma (TCC) has been attributed to direct extension, lymphatic or hematogenous dissemination, or surgical implantation. The purpose of this study was to characterize the clinical and histologic features of cutaneous TCC metastasis, confirmed by uroplakin-III immunohistochemistry, in dogs. The 12 cases were 9 spayed female and 3 neutered male dogs, 6 to 14 years old (mean, 11 years). Four dogs had a history of urinary incontinence. Three had undergone abdominal surgery for TCC diagnosis or treatment. The primary neoplasms were 7 papillary infiltrating and 5 nonpapillary infiltrating TCC. Cutaneous lesions were detected at a mean of 123 days (median, 38 days) after diagnosis of the primary TCC and appeared as plaques, papules, or nodules in, with 1 exception, perineal, inguinal, or ventral abdominal dermis or subcutis. Of 8 dogs with dermal TCC, 5 had epidermal erosion or ulceration. In 10 dogs, TCC was detected in cutaneous lymphatic vessels, identified by endothelial immunoreactivity for Prox1. Metastases were also detected in lymph nodes in all dogs and at distant noncutaneous sites, usually the lungs, in 10 dogs. Mean survival after diagnosis was 162 days (median, 90 days). Despite medical treatment of 10 dogs after the development of cutaneous metastasis, remission was not achieved; 4 dogs had stable disease. Although TCC could have spread to skin by direct extension or lymphatic or vascular dissemination, the proximity of most cutaneous metastases to the vulva or prepuce raises the additional possibility of transepidermal spread through urine-scalded skin.

A 5-month-old mongrel puppy with a history of respiratory disease presented with progressive neurologic dysfunction. Hematologic results included leukocytosis (neutrophilia with a left shift) and lymphopenia. A mass in the right forebrain, identified by magnetic resonance imaging, was biopsied during decompressive craniectomy. The histologic diagnosis was granulomatous meningoencephalitis with intralesional amoebae. The dog died within 24 hours of surgery. At necropsy, a well-demarcated granuloma was confined to the cerebrum, but granulomatous pneumonia was disseminated through all lobes of the lung. Concurrent infections included canine distemper, canine adenoviral bronchiolitis, and oral candidiasis. Canine distemper virus probably caused immunosuppression and increased susceptibility to secondary infections.