Abstract
A 33-year-old woman was admitted due to bilateral breast masses that were increasing in size. Phyllodes tumors were suspected, and a wide excision was performed. On pathology, a diagnosis of a mammary metastasis of an alveolar soft part sarcoma was made ; the diagnosis was confirmed based on the expression of a fusion transcript of ASPL-TEF3. The tumor in the right thigh was determined to be the primary ; it was resected since it was painful. Subsequently, the patient developed lung, brain, thyroid, and pancreas metastases. Alveolar soft part sarcoma is a rare soft tissue neoplasm which occurs predominantly in the lower extremities of younger adults and has unique biological characteristics. Sarcoma should be considered in the differential diagnosis of a benign-looking breast tumor with an unusual growth pattern.
