Inflammatory cellular infiltrates in melanocytic nevi

We examined 1,054 melanocytic nevi [137 (13%) simple lentigines, 158 (15%) junctional nevi, 337 (32%) compound nevi, and 422 (40%) dermal nevi] for the presence of lymphohistiocytic infiltrates. The following criteria were evaluated: age and sex of the patient, location, histological type, horizontal and vertical diameter, increase of melanocytes in the basal layer of the epidermis, increase of melanophages in the papillary dermis, melanin content of keratinocytes, and melanin content of nevus cells. Lymphohistiocytic infiltrates were measured semiquantitatively; their presence within the center, in the lateral margins, or both was also determined. The results were analyzed statistically by means of chi-square tests and univariate and multivariate analyses. We found that 824 lesions (78%) were associated with a lymphohistiocytic infiltrate; whereas 230 (22%) were not. This infiltrate was weak in 273 cases (33%), moderate in 411 cases (50%), pronounced in 130 cases (16%), and very strong in 10 cases (1%). Multivariate analyses revealed that the only criteria associated with the presence of lymphohistiocytic infiltrates were the increase of melanocytes in the basal layer and the vertical thickness in compound nevi. All other parameters were statistically insignificant. We conclude that melanocytic nevi with a junctional hyperplasia of melanocytes--i.e., mostly early stages such as simple lentigines, junctional nevi, and superficial compound nevi--are often associated with a moderate to pronounced cellular stromal reaction. Their presence may reflect the appearance of antigens on proliferating melanocytes. It may also represent a stromal reaction to necrotic tumor cells and keratinocytes within the dermoepidermal junction. These findings rule out any relationship to an increase of melanin pigment.(ABSTRACT TRUNCATED AT 250 WORDS)