Alveolar rhabdomyosarcoma mimicking nasal lymphoma at the initial presentation.

Rhabdomyosarcoma is exceedingly rare in adults. A 62-year-old woman was referred to our hospital because of general pain. Computed tomography revealed a solid tumor in the right nasal cavity. Histopathological examination showed solid proliferation of atypical small round cells, having cytologic features reminiscent of lymphomas, and lacking the fibrovascular stroma. The cells were CD56(+), desmin(+), vimentin(+), HHF35(+), myogenin(+) and MyoD1(+). The patient was positive for the PAX3-FKHR fusion gene. The patient was diagnosed as having alveolar rhabdomyosarcoma. We conclude that rhabdomyosarcoma should be included in the differential diagnoses of CD56(+) small round cell tumor, and immunohistochemical and cytogenetic studies should be performed.