CUTANEOUS MALIGNANT-MELANOMA IN SOUTH SWEDEN 1965, 1975, AND 1985 - AHISTOPATHOLOGIC REVIEW

Background. There is an increase in the incidence of cutaneous maligna nt melanoma (CMM) among white people throughout the world. In Sweden, a fivefold increase has been recorded since 1960, but the mortality is rising at a much lower rate. Tumor thickness is the single most impor tant prognostic factor for primary melanoma. This study aimed to clari fy whether the thickness of the tumor in invasive CMM decreased during the period 1965-1985. Methods. This population-based study identified 574 cases of CMM, both invasive and noninvasive, in the South Swedish Health Care Region in 1965, 1975, and 1985. Twenty-six cases were exc luded because the collection or evaluation of the material was not pos sible. The remaining 548 cases were reviewed histopathologically, and a diagnosis of invasive CMM was rejected in 71 cases. Eventually, 467 cases of invasive melanoma remained in our study (70 in 1965, 124 in 1 975, and 273 in 1985). The level of invasion, tumor thickness, regress ion, ulceration, presence of inflammatory cells, benign naevus cells, and the site of presentation were studied. Results. The study found ne ither a significant decrease of tumor thickness of invasive CMM nor ch anges in the level of invasion or proportion of ulcerated melanoma. A significantly higher proportion of melanoma tumors containing benign n aevus cells was seen throughout the years (P < 0.05). Women had signif icantly fewer inflammatory cells in their tumors than did men (P < 0.0 1). As expected, the anatomical site of presentation showed a signific ant sex-related difference, with more tumors on the legs of female pat ients and more on the trunk of male patients (P < 0.001). Conclusions. There is a divergence between the rapidly increasing incidence and th e slower increase in mortality of CMM. This cannot be explained by a r emoval of the melanoma at a thinner thickness. Differences between the sexes according to the tumor site and the increasing rate of CMM cont aining benign naevus cells could implicate changes in the tumor biolog y. Public education in Sweden concerning ultraviolet radiation and the connection with melanoma is fairly new and might not have any influen ce on this time period. Additional investigation is needed to clarify this matter.