Malignant pilomatricoma in a dog

Area of Science:

• Veterinary Pathology
• Canine Oncology
• Dermatopathology

Background:

• Malignant pilomatricoma is an uncommon skin tumor in dogs.
• Previous reports have not documented widespread metastasis of this tumor type.

Observation:

• An 11-year-old German shepherd presented with left forelimb lameness, hindlimb ataxia, and a prescapular mass.
• Radiography and necropsy revealed metastatic lesions in the humerus, lungs, liver, spleen, and lumbar vertebrae.
• Histopathology showed a basal cell proliferation with characteristic 'ghost' cells.

Findings:

• A definitive diagnosis of malignant pilomatricoma was established.
• The tumor exhibited extensive metastasis, including to the spleen and liver, which is unprecedented in canine cases.
• Bone lysis was evident in the humerus and lumbar vertebrae.

Implications:

• This case highlights the aggressive metastatic potential of malignant pilomatricoma in dogs.
• The findings expand the known metastatic patterns for this rare canine neoplasm.
• Early detection and understanding of metastatic potential are crucial for managing canine malignant pilomatricoma.