Breast cancer coexisting with lymphoma is a rare condition with various diagnostic and therapeutic implications. In this report, we describe the case of a 55-year-old Caucasian woman who presented with simultaneous ductal carcinoma in situ of the right breast, and follicular lymphoma involving an inguinal lymph node and the left breast. The patient underwent local excision and radiotherapy for the ductal carcinoma in situ, while a watch and wait strategy was adopted for the lymphoma. Two years later, the patient presented with multifocal ductal carcinoma of the left breast and reappearance of the lymphoma in the left axillary lymph nodes. She underwent bilateral mastectomy, left sentinel node biopsy, and chemotherapy. Synchronous follicular lymphoma and bilateral metachronous breast carcinoma has not been described previously. Diagnosis is based on tissue histology after excision or a needle biopsy. Treatment for these two diseases is distinct, and a multidisciplinary approach should be adopted.