Primary Leiomyosarcoma of the Breast: A Successful Surgical Treatment in a 45-Year-Old Woman.

BACKGROUND Spindle cell carcinomas and sarcomas are 2 uncommon primary spindle cell malignant tumors of the breast. Histopathology and immunohistochemistry for cell phenotypic markers can identify the type of tumor. This report is of a 45-year-old woman with a primary leiomyosarcoma of the breast, successfully treated by surgical excision. CASE REPORT A 45-year-old woman presented to our clinic in February 2018 with a 10.5-cm tumor in the right breast with lateral invasion of the pectoralis minor and pectoralis major. When the tumor first appeared in 2016, it was 5 cm in size and was diagnosed pathologically as a sarcoma. On immunohistochemical examination, the tumor cells were positive for smooth muscle actin, and vimentin with Ki 67 index of 15-20%. Previous treatment with 10 cycles of Gemcitabine was unsuccessful and showed rapid tumor growth up to 18 cm in May 2018. The patient underwent total right mastectomy with excision of the pectoralis minor muscle and partial excision of pectoral major muscle with axillary lymph node dissection. Pathological assessment revealed a necrotic mass 21.0×16.0×12.0 cm in size with invasion into the overlying breast skin and pectoralis major muscle with 2 out of 20 axillary lymph nodes with tumor growth. CONCLUSIONS This study has demonstrated the value of immunohistochemistry and histology in the diagnosis of primary spindle cell malignant breast cancers. To decrease the chance of recurrence and improve patient outcomes, primary leiomyosarcoma of the breast should be removed with a sufficient excision margin.