Natural killer cells in cutaneous malignant melanoma

Using immunocytochemical techniques on fresh surgical samples, a series of 16 cases of cutaneous malignant melanoma (CMM) were examined to characterize further the host inflammatory response. Antibodies to the following cluster of differentiation (CD) antigens were used: CD-3, CD-4, CD-8 (T-cell markers), CD-11b, CD-14 (macrophage marker), CD-16 [an antigen expressed by natural killer (NK) cells and granulocytes], and CD-25. Also examined were a small number of other melanocytic lesions [two cases of lentigo maligna (Hutchinson's melanotic freckle) and five of intradermal naevi]. The results of the study document a population of cells with the morphological and immunophenotypic characteristics of NK cells in association with 10 of the 16 cases of CMM. These cells were consistently absent from the other melanocytic lesions studied. The presence of NK cells in association with some cases of CMM bears no clear relationship to the Breslow thickness, Clark level, tumour ulceration, or the presence of activated T cells as determined by expression of the CD-25 antigen. Whilst an explanation for the significant numbers of NK cells in some CMM lesions in unclear, their presence in intimate association with tumour cells does prompt speculation regarding a possible role in determining the biological behaviour of the tumour. Additionally, the study has confirmed and extended previous findings with respect to the broad characterization of mononuclear cells present in the host infiltrate associated with CMM.