Primary Ewings Sarcoma/Primitive Neuroectodermal Tumor (PNET) of the Breast: a Rare Tumor

Abstract

Extra osseous Ewing’s sarcoma (EES) is regarded as a member of Ewing’s sarcoma family of tumors (ESFT). A 16-year-old lady presented to the outpatient department of our institute with awareness of progressively increasing lump in the right breast of 5 months duration. Biopsy from the lump done elsewhere was suggestive of poorly differentiated malignancy. On examination, there was a large mass occupying almost the entire right breast. Computed tomography scan (chest) showed a large well-defined minimally enhancing heterogeneous soft tissue lesion of size 17.3 × 14.6 × 14.4 cm in the right breast. Both lungs were normal. Metastatic work up was within normal limits. Review of the biopsy at our center showed fragmented tissue exhibiting sheets of monotonous population of round cells with dark staining nuclei with mitotic figures and minimal cytoplasm. On immunohistochemical (IHC) analysis, the neoplastic cells exhibited CD99 and Friend leukemia integration 1 (FLI1) positivity whereas they were negative for leucocyte common antigen (LCA), desmin, and myogenin, which was consistent with Ewing’s sarcoma/PNET family of tumor. She received 2 cycles of neoadjuvant chemotherapy with VAC (vincristine, doxorubicin, cyclophosphamide) + IE (ifosfamide, etoposide) alternately following which simple mastectomy with latissimus dorsi myocutaneous flap reconstruction was done. Less than 4 cases of EES of the breast have been documented in Indian literature so far. In this report, we discuss the clinicopathological features of this rare and fascinating tumor with a brief review of literature.