[Primary Rhabdomyosarcoma of the Breast in a 16-Year-Old Girl]

We report a case of primary breast rhabdomyosarcoma. A 16-year-old girl noticed tumor of her right breast and consulted a local clinic. From the result of core needle biopsy, breast sarcoma was suspected, so she attended our hospital. Breast ultrasonography showed a mosaic pattern tumor occupying the whole right breast. CT images revealed an axillary node metastasis and no distant organ metastasis. Immunohistochemical staining of the tumor yielded positive results for desmin, MyoD1, and myogenin. Based on reverse transcription polymerase chain reaction(RT-PCR), she was diagnosed as an alveolar rhabdomyosarcoma with PAX3-FKHR(FOXO1)fusion transcripts[t(2;13)(q35;q14)]. She underwent total mastectomy and dissection of axillary lymph nodes. After surgery, the whole-body magnetic resonance imaging(MRI) demonstrated metastases of sacrum and left foot, so she was under systemic chemotherapy.