Auricular rhabdomyosarcoma in a rat.

Area of Science:

• Veterinary Pathology
• Oncology
• Rattus norvegicus Research

Background:

• Neoplasms in laboratory animals require thorough characterization for comparative pathology.
• Auricular tumors are uncommon in rodent models.

Observation:

• A firm, white, 0.5 x 0.5 cm ear neoplasm was surgically removed from a 1-year-old male rat.
• Histological examination revealed an expansile, non-encapsulated tumor with pleomorphic polygonal to spindle-shaped cells and multinucleation.

Findings:

• Immunohistochemical and histochemical stains showed neoplastic cell positivity for vimentin, myoglobin, phosphotungstic acid haematoxylin, and desmin.
• Absence of immunoreactivity for cytokeratin and alpha-smooth muscle actin supported the diagnosis.

Implications:

• This case represents the first detailed description of auricular rhabdomyosarcoma in a rat.
• Findings contribute to the understanding of rare tumor types in animal models and comparative oncology.