Metastatic apocrine sweat gland adenocarcinoma in a terrier dog

This report describes the clinical and pathological aspects of an apocrine sweat gland carcinoma with distant metastasis in an aged dog. A 7-year-old male terrier dog was referred to small animal hospital of Shahid Bahonar University of Kerman with a 5.5×3.5 centimeter pedunculated mass on its head near left auricular region which had been progressively growing since three months ago. The radiography showed no local and distant metastasis. Surgical excision and histological evaluation was done. Histologically, the mass was composed of epithelial cells arranged in glandular and solid patterns. The morphologic findings suggested either a primary or metastatic apocrine-gland carcinoma. Immunohistochemically, the tumor cells were intensely positive for cytokeratin 7 and 20 and negative for S100 protein. On the basis of histopathological and clinical findings, the tumor was diagnosed as a malignant apocrine gland tumor, arising from apocrine sweat glands of the skin. Local tumor recurrence with anorexia and weight loss was reported by the owner nine month later. Severe submandibular and prescapular lymphadenomegaly was noted in clinical examination. Several large pulmonary nodules were noted in chest radiographs resembling mediastinal lymph node metastasis. Second surgery and chemotherapy was rejected by the owner due to grave prognosis of the patient. The animal was died 45 days later due to respiratory complications. Tumors of apocrine sweat glands are relatively uncommon in dogs whereas apocrine gland adenocarcinoma with distant metastasis is extremely rare.