Embryonal rhabdomyosarcoma arising in the buccal mucosa: a case report with immunohistochemical and electronmicroscopic findings.

Rhabdomyosarcoma is one of the most common soft-tissue neoplasms in children. We report a case of a 9-year-old female with embryonal rhabdomyosarcoma arising in the buccal region with immunohistochemical and electronmicroscopic findings. Under a light microscope, it was observed that the tumor was composed of small round or spindle-shaped cells with pleomorphic and hyperchromatic nuclei. They were immunoreactive for actin, myoglobin and desmin. With an electron microscope, it was found that most tumor cells contained filamentous structures and free ribosomes. Some of them showed typical myofilaments, M-bands and Z-lines. These findings were specific evidence of rhabdomyosarcoma. Twenty courses of VAC (vincristine, D-actinomycin and cyclophosphamide) chemotherapy were administered, followed by surgical resection of the tumor.