Background: There is a worldwide increase in the incidence of cutaneous malignant melanoma (CMM) among whites. In Sweden, a five-fold increase has been recorded since 1960, although the increase in mortality rate is substantially lower. Tumor thickness is recognized as the most important histologic prognostic factor for primary melanoma. In a previous study, the authors did not find any significant decrease in mean tumor thickness over the period 1965-1985 in their region. In the current study, prognostic factors for melanoma were evaluated for this time period.
Methods: In a population-based study, 468 cases of invasive melanoma, diagnosed in the years 1965, 1975, and 1985, were histopathologically reexamined. The level of invasion, tumor thickness, regressive reaction, ulceration, presence of inflammatory cells, presence of benign nevus cells, and site of presentation were studied. In 461 of these 468 patients, it was possible to correlate the histopathologic factors with survival.
Results: In univariate analyses, the parameters of presence of ulceration, increasing tumor thickness, male gender, nodular type of melanoma, and older age at diagnosis were significantly related to a shortened overall survival. In various multivariate models with adjustment for age and the factors studied simultaneously, ulceration, increasing tumor thickness, and male gender were significantly associated with a poor prognosis. Correlations between the factors studied were noted. It was observed that older patients tended to have thicker tumors. Thick melanomas correlated to a deeper level of invasion (Clark's), nodular growth pattern, ulceration, less inflammation, and less regression compared with thin, less invasive melanomas. Women had significantly fewer inflammatory cells and fewer signs of regression in their tumors compared with men.
Conclusions: In multivariate analyses adjusted for age, increasing tumor thickness, older age, ulceration, and male gender were significantly associated with a poor prognosis among patients with invasive CMM. None of these factors showed a significant change for the years 1965, 1975, and 1985. Thus, a change in the prognostic factors studied does not explain the increased survival of melanoma patients for this time period.