Primary Leiomyosarcoma of the Breast Papilla: A Case Report

Background: Breast leiomyosarcoma is a rare subtype of breast sarcoma, constituting 5–10% of the cases. Less than one-third of reported cases are located in the nipple papillary region, making it an extraordinarily rare malignancy, responsible for less than 0.1% of all malignant breast tumors. As no radiological criteria allow definitive diagnosis of papillary leiomyosarcoma, histopathological and immunohistochemical examination of suspicious lesions is required. The prognosis is generally optimistic compared with those for other breast sarcomas. Case presentation: A 54-year-old previously healthy woman reported the appearance of a nodule in her right nipple in the preceding 9 months, associated with pruritus. Physical examination revealed that the lesion had a cystic consistency and measured approximately 3.0 cm. Imaging examinations showed no involvement of the adjacent breast parenchyma or axillary region and the lesion was classified as Breast Imaging-Reporting and Data System (BI-RADS) category IV. The lesion was excised, and the histopathological diagnosis was well-differentiated leiomyosarcoma of the mammary papilla, with immunohistochemical examination showing positivity for smooth-muscle tissue antigens. A staging CT examination was performed, showing no evidence of distant metastasis. After 2 years of follow-up, the patient shows no sign of tumor recurrence. Conclusion: Although rare, leiomyosarcoma must be included in differential diagnosis of breast masses, especially those involving the periareolar region. Due to its good prognosis, reporting on this type of tumor is important to guide therapeutic planning, and to identify and track possible complications of its underdiagnosis.