Embryonal rhabdomyosarcoma in a Siberian chipmunk (Tamias sibiricus): a case report

A 2-year-old female Siberian chipmunk (Tamias sibiricus) was presented to the veterinary clinic for swelling, pain and lameness of the left rear leg. Radiologically, an invasive tumour around the distal femur was suspected, and the leg was surgically amputated and submitted for histopathological diagnosis. Microscopically, the mass was densely packed with multinucleated strap cells that had round-to-oval, or elongated nuclei with prominent nucleoli. These neoplastic cells occasionally formed myotubes with cross-striations and were immunohistochemically positive for muscle markers including desmin and myogenin. Consequently, embryonal rhabdomyosaroma myotubular variant of the leg with metastasis to the femur was diagnosed. Spontaneous rhabdomyosaromas are rare tumours in animals and humans, and this is the first report of its occurrence in a Siberian chipmunk.