Alveolar soft part sarcoma metastatic to the breast: a case report.

Background: Alveolar soft part sarcoma (ASPS) is an extremely rare neoplasm that tends to occur in the lower limbs of children and adolescents. Metastatic breast tumors constitute 0.5-2.0% of all malignant mammary neoplasms, and cases of ASPS with mammary metastases are very rare.
Case Presentation: Three years ago, an 11-year-old girl presented to the hospital with pain in the right jaw after becoming aware of a mass in the right cheek. After detailed examination, the patient was diagnosed with ASPS with the primary tumor in the right cheek and multiple lung metastases, and chemotherapeutic treatment was initiated. One year later, accumulation of fluorodeoxyglucose (FDG) was observed in the right front of the skull (standardized uptake value (SUV)-max 2.8) and left breast (SUV-max 2.4) using FDG-positron emission tomography (PET) / computed tomography (CT). Ultrasonography revealed the mammary tumor as a hypoechoic, internally heterogeneous mass measuring 22.4 × 16.2 × 21.1 mm with a rich blood supply. Using pathological findings of core-needle biopsy, we diagnosed it as ASPS. Based on the above information, we made a diagnosis of ASPS with left mammary and cranial metastases. Due to chemoresistance, surgical excision was selected as the mode of treatment; resection of the metastatic cranial bone was performed first, and partial mastectomy of the left breast was performed in two stages. Postoperative conditions were good, and we are currently performing regular follow-ups (visual palpation every 3 months and semi-annual mammary gland ultrasonography).
Conclusions: We have reported an extremely rare case of ASPS with mammary metastasis with some reference-based discussion. In our case, disease control was obtained by a combination of drug therapy and surgical treatment.