Synchronous presentation of breast carcinoma and non-Hodgkin lymphoma (NHL) is a rare occurrence (Bradford PT, Freedman DM, Goldstein AM, Tucker MA. Increased risk of second primary cancers after a diagnosis of melanoma. Arch Dermatol 2010; 146: :265-72; Dutta Roy S, Stafford JA, Scally J, Selvachandran SN. A rare case of breast carcinoma co-existing with axillary mantle cell lymphoma. World J Surg Oncol 2003; 1: :27; Suresh Attili VS, Dadhich HK, Rao CR, Bapsy PP, Batra U, Anupama G et al. A case of breast cancer coexisting with B-cell follicular lymphoma. Austral Asian J Cancer 2007; 6: :155-6). In particular, only two reported cases on synchronous presentation of invasive ductal carcinoma (IDC) and mantle cell lymphoma (MCL) exist in the English literature. Owing to the rarity, there is a lack of consensus about underlying mechanism as well as optimal treatment strategy, and diagnosing both malignancies together without a delay remains a complex clinical challenge. We report a case of synchronous presentation of IDC and MCL in a 67-year-old female patient whose MCL diagnosis was delayed due to a misinterpretation of her B symptoms as postmenopausal, with a review of the literature on concurrently occurring breast carcinoma and NHL.