LAUSR

Metastases to the breast are rare (less than 3% of all breast malignancies). In adults, malignant melanoma is the most common type of metastasis followed by carcinomas from various primary sites. Here, we describe a case of metastatic alveolar soft part sarcoma (ASPS) to the breast. Only a handful similar presentations are reported in the literature. Here we describe the case of a 43-year-old female patient with a recent diagnosis of left base of tongue alveolar soft part sarcoma (in an outside hospital), presenting with a palpable mass in her left breast. Sonographic study of the left breast demonstrated a 1.4 cm oval hypoechoic mass with partially microlobulated margins at 1 o’clock. Histopathologic examination of the ultrasound guided core biopsy showed a “pink” neoplasm, composed of plump epithelioid tumor cells with an eosinophilic and granular cytoplasm, round to oval nuclei and conspicuous nucleoli. They are arranged in organoid nests separated by sinusoidal spaces. An immunohistochemical study shows the tumor cells to be negative for keratin AE1/AE3, keratin 7, keratin 5/6, GATA-3, Pax-8, estrogen receptor, HER2, p63, S100 and CD117. FISH test for TFE3 (Xp 11.23) is positive. PAS with diastase staining highlights the intracytoplasmic granules. Theses morphologic, clinical and molecular findings confirm the diagnosis of metastatic ASPS. The differential diagnosis of “pink” tumors of the breast include primary tumors like secretory carcinoma and apocrine carcinoma and metastatic lesions of renal, thyroid, skin (melanoma), oral cavity and soft tissue. Although extremely rare, in the right clinical context, metastatic ASPS to the breast can occur and should be included in the differential diagnosis.