Subcutaneous soft tissue sarcoma with rhabdoid features in a dog

Area of Science:

• Veterinary Pathology
• Canine Oncology
• Soft Tissue Tumors

Background:

• Soft tissue sarcomas are a diverse group of tumors affecting mesenchymal cells.
• Rhabdoid features in tumors can present diagnostic challenges due to their unique morphology.
• Accurate classification is crucial for prognosis and treatment in veterinary oncology.

Observation:

• A nine-year-old male beagle presented with a subcutaneous white spherical mass in the left lumbar region.
• Microscopic examination revealed diffuse proliferation of spindle to oval cells within a fibrous and myxoid stroma.
• Neoplastic cells displayed rhabdoid features and vacuolated cytoplasm.

Findings:

• Immunohistochemistry showed positivity for vimentin, S100, and partial positivity for neuron-specific enolase and glial fibrillary acidic protein.
• Neoplastic cells were negative for von Willebrand factor, desmin, and α-smooth muscle actin.
• Ultrastructural analysis revealed cytoplasmic processes and desmosome-like structures; cytoplasmic inclusions were intermediate filaments, and vacuoles were cytoplasmic invaginations.

Implications:

• The tumor was diagnosed as a soft tissue sarcoma with rhabdoid features, differentiating it from a potential malignant peripheral nerve sheath tumor.
• This case highlights the importance of integrating morphological, immunohistochemical, and ultrastructural findings for accurate diagnosis in challenging veterinary tumor cases.
• Understanding these rare canine neoplasms contributes to the broader knowledge of soft tissue sarcoma in comparative oncology.