Rhabdomyosarcoma of the skin resembling carcinosarcoma: report of a case and literature review.

Rhabdomyosarcomas (RMSs) are soft tissue sarcomas with skeletal muscle differentiation. Cutaneous RMSs are exceedingly rare, and in most cases, they represent metastatic disease or the dermal involvement by a tumor arising in the underlying soft tissues. We herein report the case of a 41-year-old man who developed a cutaneous swelling of the right nasal orbital angle. An initial incisional biopsy showed cytokeratin-positive atypical spindle cells forming long and intersecting fascicles, thus the case was diagnosed as carcinosarcoma. In the subsequent excisional biopsy, the skeletal myogenic differentiation of the tumor cells infiltrating the dermis and subcutis was demonstrated by morphology (presence of rhabdomyoblasts), immunohistochemistry (positivity for desmin, myogenin, myoglobin, and actins), and electron microscopy (evidence of rudimentary sarcomeric structures). A final diagnosis of primary cutaneous RMS was made. The patient was subjected to postoperative radiation and chemotherapy, but after 4 months, the patient developed a tumor recurrence followed by distant metastases and death. Review of the literature reveals that RMSs of the skin are often underrecognized and display peculiar clinical features in comparison with their more common soft tissue counterpart.