RESUMEN
BACKGROUND The incidence of multiple primaries in cancer patients is 2-17%. However, the synchronous co-occurrence of adenocarcinoma of the breast and follicular lymphoma is rare. CASE REPORT We describe a case series of 3 post-menopausal women who presented to our institute with a breast lump. On further investigations, 2 of them had invasive ductal carcinoma and 1 had invasive lobular carcinoma of the breast. All 3 cancers were estrogen/progesterone receptor (ER/PR)-positive and human epidermal growth factor receptor 2 (HER-2)-negative. During the staging PET scans, all 3 patients had increased FDG uptake in axillary, mesenteric, and inguinal lymph nodes, respectively, raising concerns for metastatic disease. However, subsequent biopsies revealed them as follicular lymphomas occurring as a second concurrent primary malignancy. All patients underwent radical mastectomies with sentinel lymph node dissection followed by chemotherapy and hormonal therapy. Most of the lymphomas were low grade, which the oncologist closely followed. CONCLUSIONS Very few cases of breast cancer and follicular lymphoma co-occur; this is not limited to the axillary lymph nodes and can occur in any part of the lymphatic chain. Regional lymph node enlargement detected on examination or imaging does not always indicate metastasis. A high index of suspicion is needed followed by lymph node biopsy to rule out any second primary malignancy.