Prognostic factors in localized invasive primary cutaneous malignant melanoma: results of a large population-based study

BackgroundThe prognostic impact of several histopathological prognostic features in cutaneous malignant melanoma (CMM) remains controversial. ObjectivesTo assess the independent prognostic value of mitotic rate, regression, tumour-infiltrating lymphocytes (TILs) and growth phase in primary stage I and II CMMs. MethodsClinicohistopathological data were obtained from the Stockholm-Gotland registry for 4237 patients diagnosed with an incident primary stage I or II CMM followed up to December 2011. The risk of CMM-specific death was evaluated by a Cox regression model. ResultsA mitotic rate of 1-10 mitoses per mm(2) [hazard ratio (HR) 169, 95% confidence interval (CI) 116-245] and >10mitoses per mm(2) (HR 227, 95% CI 146-352) were significant; TILs and regression were not. A more detailed analysis of data assessed between 1989 and 1995 confirmed significantly increased HRs for the presence vs. absence of mitoses (HR1-5/mm2 225, 95% CI 136-376; HR6-10/mm2 234, 95% CI 123-444; HR>10/mm2 264, 95% CI 139-499). Other prognosticators were increasing T-stage vs. T1, presence of ulceration and presence of vertical growth phase (VGP). In T1 CMMs, an increasing tumour thickness vs. <07mm (HR07-08mm 224, 95% CI 124-404; HR(>08mm)292, 95% CI 157-543) and presence of ulceration were significantly associated with higher HRs; mitotic rate, TILs, regression and growth phase were not. ConclusionsDeterminants of increased risk of CMM death in stage I and II CMMs were increasing T-stage, presence of ulceration, presence of mitoses and VGP. This was not found for TILs or regression.