Epithelioid rhabdomyosarcoma: Report of the first case in the jaw.

OBJECTIVES

Epithelioid rhabdomyosarcoma (EpiRMS) is a novel morphologically distinct variant of rhabdomyosarcoma, with an unusually challenging microscopic diagnosis. The occurrence of rhabdomyosarcomas in the jaws is extremely rare. This study presents the first case of EpiRMS in the jaw (mandible) and a literature review of the previous 35 cases of EpiRMS.

STUDY DESIGN

Here, we report a case of EpiRMS affecting an 18-year-old male patient. Clinical, imaging, microscopic, and immunohistochemical features are discussed and previously reported cases of EpiRMS are reviewed.

RESULTS

An 18-year-old male patient presented with an exophytic sessile growth on the buccal gingiva, and orthopantomography revealed irregular bone loss. Microscopic analysis showed a large number of cells with epithelioid appearance. Immunohistochemistry staining was positive for desmin, myogenin, MyoD1, smooth muscle actin, h-caldesmon, INI-1, and AE1-AE3. The patient's disease was staged as T4aN1M0 and was treated with surgical excision combined with chemotherapy.

CONCLUSIONS

The occurrence of RMS in the mandible is rare, and this is the first case of EpiRMS in the jaw. EpiRMS is an unusual histologic subtype that mimics other sarcomas and epithelial malignancies, making diagnosis a challenge. A specific immunohistochemistry panel aids in the diagnosis. EpiRMS has an aggressive course and an unfavorable prognosis.