Diffuse Large B-cell Lymphoma of the Breast Presenting 40 Years After Breast-Conserving Therapy: A Case Report.

Breast-conserving surgery combined with radiotherapy has been established as a standard therapeutic option for the management of early-stage breast cancer. Although radiation-associated tumors most frequently include sarcomas, lung cancer, and contralateral breast carcinoma, lymphoid malignancies arising within previously irradiated breast tissue are rarely reported. Breast lymphoma is a rare entity, and its occurrence following prior treatment for breast cancer may pose a diagnostic challenge as it can mimic recurrence of the primary malignancy. We report a case of diffuse large B-cell lymphoma of the breast in an 88-year-old woman presenting approximately 40 years after breast-conserving surgery and radiotherapy for invasive ductal carcinoma. The lesion was initially suspected to represent recurrent breast cancer based on clinical and imaging findings; however, histopathological and immunohistochemical evaluation confirmed lymphoma. Although the tumor arose within a previously irradiated field, a causal relationship with prior radiotherapy could be established and should be interpreted with caution. This case highlights the importance of considering alternative diagnoses in patients presenting with new breast lesions long after initial cancer treatment, particularly in elderly individuals.