A principal case of multiple lymphoid collision tumors involving both B-cell chronic lymphocytic leukemia and metastatic malignant melanoma.

B-cell chronic lymphocytic leukemia/small lymphocytic B-cell lymphoma (CLL/B-SLL) is a neoplasm of B-cell lymphocytes that occurs frequently in the older population as an asymptomatic elevation of the white blood cell count (WBC) and has a good overall prognosis. Malignant melanoma of the skin is a neoplasm derived from cutaneous melanocytes that frequently arises among the elderly and, depending on certain histopathologic features, may metastasize loco-regionally or distally. However, only one report describes synchronous presentation of these two malignancies within the same lymph node. In this report, we present the unique case of an 87-year-old male with a presumed history of indolent CLL/B-SLL, in which metastatic malignant melanoma and CLL/B-SLL both involved 112 of 145 dissected regional lymph nodes. Possible explanations regarding the mechanisms that can lead to this rare presentation of both CLL/B-SLL and melanoma in the same lymph nodes are discussed.