Major Histotypes in Skin Melanoma: Nodular and Acral Lentiginous Melanomas Are Poor Prognostic Factors for Relapse and Survival.

The histological subtype is not considered one of the major prognostic factors in melanoma, yet it is known to have an impact on survival. The aim of this study was to investigate the clinical significance of histological subtypes and the possible impacts of clinicopathological factors on the course of melanoma patients of all stages. A total of 1017 cutaneous melanoma patients were analyzed retrospectively. Four major melanoma histotypes that were studied in this study were as follows: (1) superficial spreading melanoma (SSM), (2) nodular melanoma (NM), (3) acral lentiginous melanoma (ALM), and (4) lentigo maligna melanoma (LMM). Unlike SSMs and LMMs, there were statistically significant correlations between NMs and ALMs and most aggressive histopathological prognostic indicators, such as higher Clark level ( P = 0.0001), thick Breslow depth ( P = 0.0001), presence of ulceration ( P = 0.0001), and lymphovascular invasion ( P = 0.0001). Furthermore, NMs and ALMs were also associated with advanced clinical stages, that is, node involvement and metastasis. Relapse rates for nonmetastatic melanomas were higher in NMs (39.6%) and ALMs (35.3%) than in SSMs (24.3%) and LMMs (10.3%) ( P = 0.0001). Additionally, 5-year relapse-free survival rates were 90.5%, 70.5%, 55.7%, and 50.5% in LMMs, SSMs, ALMs, and NMs, respectively ( P = 0.0001). Moreover, 5-year overall survival rates plummeted from 84.3% in LMMs to 74.8%, 64.3%, and 46% in SSMs, ALMs, and NMs, respectively ( P = 0.0001). In conclusion, we observed that the histologic subtype was an independent predictor for relapse and outcome for cutaneous melanoma patients. Both NM and ALM had unfavorable prognoses, and they were associated with known poor pathological and clinical indicators.