Invasive spindle-cell rhabdomyosarcoma with osteolysis in a dog: case report and literature review

Abstract

Rhabdomyosarcoma (RMS), a malignant mesenchymal neoplasm derived from skeletal muscle, is relatively rare in both human and veterinary medicine. Here we report an unusual case of invasive spindle-cell RMS (SCRMS) with bone infiltration and pathologic fracture in a 3.5-y-old intact female Bulldog. Radiographically, a large, predominantly osteolytic mass in the tibia and fibula of the left hindlimb had features typical of a malignant primary bone tumor. Clinically, osteosarcoma was suspected, and the leg was amputated. Histologically, the mass was composed of loosely interwoven spindle-cell fascicles; tumor cells were fusiform with cigar-shaped nuclei and abundant eosinophilic cytoplasm. The neoplastic cells were strongly immunopositive for vimentin, muscle-specific actin, desmin, myogenin, and myoD1. Invasive SCRMS with osteolysis was diagnosed based on the histologic examination and immunohistochemical (IHC) stains. The dog was alive without any evidence of local recurrence or distant metastasis 18 mo post-surgery. RMS should be included in the differential diagnosis when osteolysis occurs; IHC staining confirmation is of great value for definitive diagnosis and treatment planning.

Surgical management of a laryngeal rhabdomyosarcoma in a cat

“…These markers may be particularly helpful in the identification of poorly differentiated RMS. 16 An interesting finding in this report was the propensity and speed with which the mass was noted to recur following cytoreduction. Following each intervention, there was resolution of clinical signs for 4-8 weeks.…”

“… 13 , 14 Based on the current human medical literature and with application of data with respect to RMS in general, the optimal therapy may be a multimodal approach consisting of surgery (partial or total laryngectomy) followed by chemo- and/or radiotherapy. 14 , 15 Histologically, these tumours are categorised into embryonal, alveolar, botryoid and pleomorphic forms, as well as a rare spindle-cell variant, 16 based on the medical pathology literature. Immunohistochemistry can increase the certainty of diagnosis with positive findings for muscle-specific actin, desmin and myoglobin, which are markers of mature muscle cells.…”