Collision breast tumors, consisting of breast cancer (BC) and non-Hodgkin's lymphoma (NHL), are extremely rare. Here we report the case of a 64-year-old woman with a collision tumor in her left breast mass that was composed of invasive ductal carcinoma and small lymphocytic lymphoma/chronic lymphocytic leukemia. In addition, we reviewed the published comparable English-language literature. Collision breast tumor composed of BC and NHL is extremely rare. For that reason, there is a lack of consensus about the underlying mechanism, and diagnosing it without delay remains a complex clinical challenge. We found that post-menopausal, age-related estrogen levels changes and Epstein-Barr virus infection are possible pathogenic factors. However, the symptoms are almost identical, and it is difficult to distinguish a simple breast tumor from a breast collision tumor. In this study, we reviewed the clinical features of all patients with BC and NHL colliding breast tumors; this information might enable early identification and prevention of misdiagnosis.