Quantitative alterations in cutaneous Langerhans cells during the evolution of malignant melanoma of the skin.

Melanomas are associated with a T-cell predominant infiltrate that may cause their regression. Langerhans cells (LC) are essential for initiation and maintenance of specific T-cell-mediate responses in the skin. Therefore, a change in this antigen-presenting LC population may alter the host response. To determine whether the LC population varies during the evolution of primary cutaneous melanoma 32 melanocytic lesions, nevi, and cutaneous melanomas were studied by quantitative immunohistology. The monoclonal antibody, Leu-6, and the avidin biotin complex immunoperoxidase method were used to identify LC. Compared with histologically normal melanoma-adjacent skin, epidermal LC were depleted above "deeply invasive" melanomas but were relatively unchanged above nevi, "early invasive" melanomas, and cutaneous metastatic melanoma nodules. Dermal LC were significantly increased around in situ and "early invasive" melanomas but not around "deeply invasive" melanomas or cutaneous metastatic nodules. Dermal LC are thus associated with early transformed melanocytes and may present neoantigens to T lymphocytes in situ or after LC maturation in the draining lymph node. Melanoma-associated LC decline in number as melanoma progresses.