Synchronous occurrence of primary breast cancer and renal cell carcinoma: A case report and literature review

Multiple Primary Malignant Neoplasms (MPMNs) are rare and refer to the occurrence of two or more distinct primary cancers with unrelated histopathological features in one patient. MPMNs can be classified as synchronous when tumors appear simultaneously or within six months of each other, and as metachronous when identified six months or more after the initial cancer diagnosis. While breast cancer often co-occurs with other primary cancers such as colorectal, endometrial, and ovarian cancers, the simultaneous presence of invasive lobular breast carcinoma and clear cell renal cancer is rare.