Patterned distribution of metastases from malignant melanoma in humans

Malignant melanoma has an unpredictable clinical course in terms of metastatic behavior, and further understanding might lead to improved therapeutic intervention with immune agents or antagonists. To determine whether metastases show patterns or are randomly distributed, we analyzed the distributions of metastases in the 56 patients with metastatic malignant melanoma, subjected to complete autopsy at The Johns Hopkins Hospital, using parametric statistics and cluster analysis. Variables examined included age, race, sex, location of primary tumor, length of survival, mode of therapy, histology of tumor, location of metastases, and extent of tumor infiltration at each metastatic site. The results indicate that the distributions of metastases from malignant melanoma are patterned such that significant positive correlations (p <0.05 or better) were observed among various tissues and organs. We identified several aggregations with respect to the distributions of metastases: (a) central nervous system; (b) mesodermal; (c) endocrine; (d) reticuloendothelial; and (e) foregut. Organs and tissues comprising each aggregation were interrelated by their similar developmental origins or functions. A very highly significant negative correlation between central nervous system and hepatic metastases (p <0.001) was also demonstrated by cluster analysis. We concluded that the distributions of metastases from malignant melanoma are not random; the patterns of metastases may be related to the embryological derivation of tissues involved.