Abstract
Synchronous breast cancer and breast lymphoma are rare. It is of high rate of misdiagnosis in clinical practice. Here we present two cases with this presentation. They are both middle-aged women, with stage I invasive ductal carcinoma of the breast. One patient happened to have primary breast lymphoma (PBL); the other was secondary breast lymphoma (SBL). Their pathology and immunohistochemistry (IHC) findings supported the diagnosis of multiple primary carcinoma. Both patients had a surgery. Then they both received CHOP regime chemotherapy and subsequent endocrine therapy.