Malignant Pilomatricoma in a Young Dog

Abstract

Malignant pilomatricoma is malignant follicular tumor with only matrical differentiation. Malignant pilomatricoma is rare in dogs. There is little information about sex, breed and age predisposition. There are a few reports of canine malignant pilomatricoma in middle to old age dogs. However, this neoplasm was resected from 1-year-old intact male miniature poodle. The neoplasm was found in the dorsal part of the neck. The mass was firm and protruded. On gross findings the size of the mass was 3×2×1.5cm. The mass was located in the deep dermis and subcutaneous layer. The mass was composed of several lobules of grey-white chalky material. Microscopically, the mass was composed of several large and small lobules. There were basophilic round to oval basaloid cells at the periphery of the lobules. The basophilic cells showed abrupt keratinization. Numerous ghost cells were observed in the center of the mass. The ghost cells had abundant eosinophilic cytoplasm without a nucleus. The basophilic basaloid cells showed numerous atypical mitotic figures. Cellularity was high and pleomorphism was remarkable. No lymphatic metastasis was observed. We reported a rare case of malignant pilomatricoma in a 1-year-old young dog.

Keywords

• malignant pilomatricoma
• mitotic atypia
• mitotic index
• young dog