Nevus cells in lymph nodes: an association with congenital cutaneous nevi.

It is known that collections of nevus cells can occur in the collagenous framework of lymph nodes excised for a variety of reasons. These can be difficult to distinguish from nodal deposits of metastatic cancer but attention to cytologic detail, the distribution of the cells, and their immunohistochemical profile usually lead to a satisfactory conclusion. From another perspective, the mechanism by which nevus cells are deposited in lymph nodes has been a source of interest and controversy. Theories in this regard include embolic transfer of cells from cutaneous nevi to corresponding regional nodes and an aberration in the embryologic migration of melanocytes in utero. There have been tentative indications in the literature of a potential link between the presence of nevus cells in lymph nodes and cutaneous nevi in corresponding catchment areas of skin. In the course of evaluating sentinel lymph nodes from patients with melanoma, we noted a significant association between the presence of nodal nevi and cutaneous nevi in corresponding regional zones of skin (Fischer's exact test, p = 0.021). The link with cutaneous nevi of congenital type was even stronger (Fischer's exact test, p = 0.008). This consolidates previous sporadic reports of such an association and through further scrutiny may help shed light on the mechanism by which nodal and congenital cutaneous nevi are linked.