A Case Report: First Report of a Primary Breast Leiomyosarcoma with Lymph Node Metastasis in Lebanon

Background: Primary leiomyosarcoma (LMS) of the breast is an extremely rare histologic subtype of malignant breast tumors. While breast sarcomas account for 0.0006% of all breast malignancies, primary leiomyosarcoma constitutes only 5-10% of breast sarcomas themselves. To date, the total number of reported cases in the literature is less than 70 cases with the first case reported in 1968. This is, to the best of our knowledge, the first case reported from Lebanon, with only 2 cases previously reported in the Middle East, specifically in Morocco. Case Report: We report the case of a 48-year-old, white, previously healthy female patient, presenting for a breast mass. She first noticed it three months prior to presentation in her left breast and reports that since then, the lump has been growing and her breast has become more painful and erythematous over time. Physical examination revealed an immobile and tender mass of around 12 cm in diameter. A core biopsy was done followed by a left modified radical mastectomy with lymph node dissection. Pathology of the specimen showed a tumor composed of spindle cells arranged in fascicles invading the dermis, with irregular nuclei and prominent nucleoli. Immunohistochemical staining confirmed the diagnosis of high-grade leiomyosarcoma. Conclusion: We presented this case of leiomyosarcoma with lymph node metastasis to contribute to the scarce literature regarding this disease. Due to the rarity of this diagnosis, not enough data exists regarding treatment and prognosis. Physicians need to review the literature for relevant cases to achieve the best outcome for their patients. Keywords: breast mass, leiomyosarcoma, rare, case report, breast sarcomas, lymph node