Lymph nodes, benign intracapsular nevic cells [LMP52427]

These lymph nodes are part of a larger specimen, from a total thyroidectomy with left neck dissection for a papillary thyroid carcinoma (tall cell variant) with radiologic suspicion of lymph node metastases.

Clinical Discussion

Nevus cell aggregates in lymph nodes have been reported since at least 1931 by Stewart and Copeland. They are found relatively commonly in sentinel lymph node specimens, including those taken to evaluate for malignant melanoma. Histologically, the nevus cells are generally found in the capsule or trabeculae of lymph nodes. Although they can be readily seen on H&E sections, immunohistochemical analysis show that these are generally positive for S-100 or MART-1, and negative or only weakly positive for HMB-45. In contrast to metastatic melanoma cells, nevus cell aggregates tend to be negative for proliferation marker Ki-67 and are surrounded by a delicate reticulin network. The basis of how these nevic cells arrived in the lymph nodes remains controversial, with hypotheses revolving around (1) arrested migration of neural crest progenitor cells and (2) mechanical transport / benign metastasis.