Malignant pilomatricoma in a dog

Histologic features of hair follicle neoplasms and cysts in dogs and cats: a diagnostic guide

Hair follicle neoplasms occur in many different species, including humans. In domestic animals, they are most common in dogs. Most hair follicle tumors are benign, but malignant neoplasms can also occur. To diagnose hair follicle neoplasms, a thorough knowledge of follicular anatomy is important, given that follicular tumors are classified according to the differentiation pattern seen in the corresponding part of the normal hair follicle. This review focuses on the key diagnostic features of hair follicle tumors and follicular cysts in dogs and cats.

Cutaneous Pilomatrical Carcinosarcoma in a Dog

Malignant pilomatricomas are uncommon cutaneous neoplasms in veterinary and human medicine. Pilomatrical carcinosarcoma is a rare subset of malignant pilomatricoma that has been described in man. This article reports a neoplasm with morphological features of pilomatrical carcinosarcoma in a dog. The nodular neoplasm occurred on the left lateral hock and was partially alopecic. Microscopically, the tumour was composed of a cystic carcinomatous component surrounding areas of abrupt keratinization and a sarcomatous component exhibiting bundles of spindle cells and irregular, scalloped areas of mineralized and non-mineralized osteoid matrix. The carcinomatous and sarcomatous areas were immunoreactive for pan-cytokeratin and vimentin, respectively, while immunoreactivity for e-cadherin was restricted to the carcinomatous component of the neoplasm. The unique morphological features of this tumour were similar to those described in human pilomatrical carcinosarcoma.

Malignant pilomatricoma in a dog with local and distant metastases treated with chemotherapy and bisphosphonates

A ten-year-old male neutered cross breed dog presented for evaluation of a mass associated with the left scapular bone, identified as a carcinoma. The dog had a malignant pilomatricoma removed from the left lateral thigh 6 months earlier. Histopathology review of the cutaneous and scapular mass identified the same tumour type, confirming metastatic disease; additional metastases to the inguinal lymph node, liver and lungs were identified. Chemotherapy resulted in partial responses/stable disease of very short duration. Bisphosphonates were administered due to lack of a measurable response and worsening of the associated lameness. The patient ultimately developed a symptomatic vertebral metastasis and was euthanased. The dog survived 255 days since medical treatment was started and 455 days since surgical removal of the primary tumour. This case report suggests that medical treatment with the addition of analgesia may be able to palliate clinical signs and possibly extend survival in dogs with metastatic epithelial cancer.

Malignant Pilomatricoma in a Young Dog

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.

IMAGING DIAGNOSIS-NUCLEAR SCINTIGRAPHIC, RADIOLOGICAL, AND PATHOLOGIC CHARACTERISTICS OF METASTATIC PILOMATRICOMA IN A DOG

A 6-year-old castrated Goldendoodle dog was presented for left-sided lameness of 3 weeks' duration. Focal, moderate to marked increased ^99m Tc-methylene diphosphonate (^99m Tc-MDP) uptake was detected in the right caudal lung lobe, caudal angle of the left scapula, and the distal aspect of the left femur with whole body bone phase scintigraphy. Radiographs identified a well-circumscribed, oval-shaped soft tissue opaque mass in the right caudal lung lobe; a suspect oval-shaped osteolytic lesion in the proximal third of the left scapula; and an osteolytic lesion in the distal aspect of the left femur. Metastatic pilomatricoma was confirmed histologically at all three sites.