Granulocytic sarcoma (GS) also called, myeloid sarcoma, chloroma, myeloblastoma or extra medullary myeloid tumor is an extra medullary hematopoietic neoplasm composed of immature myeloid cell (myeloblasts). GS may occur in leukemia, myeloproliferative disorder. GS can occur in any site of the body; common sites of involvement include bone, CNS, soft tissue, lymph nodes and skin, but breast is very rare. GS of breast have been reported both before and after hematological diagnosis. Primary, isolate or non-leukemic GS of breast was described when bone marrow biopsy to confirm as no other hematologic malignancy. Depending on review of all Medline cases reported, only 24 cases of primary were commonly in unilateral site, and only 4 cases were bilateral site. The incidence of GS of breast is 2/1,000,000 in adults and ages ranged from 16–72 years (mean 31 years). The histology was composed of homomorphous of eosinophil cytoplasm of immature cell with single or multiple nucleoli. The malignant cells were positive for myeloperoxidase (MPO), CD43, CD34, TDT, CD 117, CD68 and negative for CD20, CD30, CD3, CD56, CD79 and ULH1.The differential diagnosis included lymphoma and poorly differentiated carcinoma. The prognosis was very poor. We report a case of granulocytic sarcoma (GS) in the left breast of a 33-year-old woman who presented with breast mass, which was diagnosed as diffuse lymphoma, large cell type on H&E histopathology without any special straining, immunohistochemical and very limited of patient information such as echography, CBC, FNA or biopsy of breast or bone marrow tissue. The final diagnosis was made by additional immunohistochemical study.