Primary breast sarcomas are very rare and account less than 1% of invasive breast carcinomas. Primary sarcomas of breast are leiomyosarcoma, angiosarcoma, liposarcoma, fibrosarcoma, rhabdomyosarcoma, malignant peripheral nerve sheath tumor and pleomorphic sarcoma. Recently, a new CD10 positive group of sarcoma was identified. These tumors cannot be classified as a soft tissue sarcoma and show diffuse strong positive staining pattern with CD10 (NSCD10). Herein we report clinical and morphological characteristics of two cases diagnosed with not otherwise specified-type sarcoma with CD10 expression by histologically and immunohistochemical findings with the literature. NSCD10 shows similarity with leiomyosarcoma and sarcomatoid-type metaplastic carcinoma histomorphologically among specific sarcomas of breast. CD10 expression should be taken into consideration in the presence of not diagnosed and not specified tumors and CD10 should be added to the immunohistochemical panel.