Abstract
BACKGROUND: Undifferentiated pleomorphic sarcoma is a rare entity and requires extensive immunohistochemical markers to differentiate it from other tumors of the breast. CASE PRESENTATION: We present a 29-year-old female with a left breast lump for 2 months. Initial diagnosis of malignant spindle cell tumor was done on core biopsy following which total mastectomy was done. After extensive sampling, on histology, highly pleomorphic spindle cells palisading the area of geographic necrosis with very high atypical mitosis were seen. As there was diagnostic difficulty, immunohistochemical antibody panel was used and diagnosis of undifferentiated pleomorphic sarcoma of the breast was made by exclusion. CONCLUSIONS: Core biopsy with immunostaining is possibly superior to FNA as an initial diagnostic modality for breast masses with atypical features.