Abstract

An association between malignant melanoma and lymphoproliferative disorders has been well described. Patients with malignant melanoma have an increased risk for developing a secondary hematologic malignancy, and likewise patients with hematologic malignancies have been shown to have an increased risk for developing melanoma and non-melanoma skin carcinoma. This relationship might be linked to underlying common immunologic defect, the exact mechanisms of which have yet to be defined. Furthermore, in a limited number of patients with melanoma, lymph node specimens collected for melanoma staging purposes might harbor lymphoma or even carcinoma. The biopsied lymph node(s) might serve as the first site of recognition for a concurrent lymphoma or metastatic malignancy. Yet, there has been little investigation regarding how frequently lymphoma or carcinoma is detected incidentally on sentinel lymph node biopsy for melanoma. Instances of synchronous melanoma and lymphoma or carcinoma have been described in a few case reports featuring just one or two cases. We present a retrospective series of eight cases of lymphoma detected incidentally during sentinel lymph node biopsy for malignant melanoma staging, 37.5% (3/8) of which were first-time diagnoses of lymphoma in a patient with known melanoma. Chronic lymphocytic leukemia/small lymphocytic lymphoma was the most frequent lymphoma seen (75% of cases), with 12.5% (1/8) of cases showing concurrent melanoma lymph node metastases. We discuss the clinicopathologic features and estimate a <1% incidence of unexpectedly detecting lymphoma in a melanoma sentinel lymph node biopsy. Additionally, we share three cases of carcinoma metastases identified during our review of sentinel lymph node procedures for melanoma staging, and two of three cases were in patients without a known primary adenocarcinoma diagnosis. Awareness of the shared risk factors for melanoma and lymphoma and knowledge of the morphologic patterns of the most common lymphomas will improve diagnostic accuracy and potentially avoid missed diagnoses of new lymphoma encountered in a dermatopathology setting. To our knowledge, this is the largest series examining this unusual, but possible phenomenon.