Fine-needle aspiration diagnosis of a metastatic adult sclerosing rhabdomyosarcoma in a lymph node.

Adult sclerosing rhabdomyosarcoma (ASRMS) is a rare variant of rhabdomyosarcoma with a characteristic histological appearance of small, round cells in a dense, hyalinized stroma. Although nodal metastases of soft-tissue sarcomas are considered uncommon, up to 5% overall are associated with lymph node metastases. Nonetheless, there is little literature on the cytologic characteristics of metastatic soft-tissue sarcomas in lymph nodes, and to our knowledge, there are no reports of nodal metastasis of ASRMS diagnosed by fine-needle aspiration (FNA) cytology. We report here a 55-year-old woman who presented with a right thigh mass and associated ipsilateral inguinal lymphadenopathy. Biopsy of the mass revealed a uniform population of small, round cells in a dense, sclerotic background. A diagnosis of ASRMS was rendered. Subsequently, the patient underwent FNA of an enlarged inguinal lymph node, which revealed an identical population of small, round cells in a dense, myxoid background. This case highlights the cytologic features of a rare form of rhabdomyosarcoma, and emphasizes the utility of FNA in the assessment of lymphadenopathy in the setting of a soft-tissue sarcoma.