Prognostic role of the histological subtype of melanoma on the hands and feet in Caucasians
Acral melanoma (AM) is associated with a poor prognosis in part because of delayed diagnosis, but probably also because of other intrinsic characteristics of location. The aim of this study was to review the specific characteristics and outcome of AM in Caucasians. This was a cross-sectional retrospective clinical-pathological study of 274 patients identified with AM in the database of a referral unit in Europe from 1986 to 2010. The mean age of the patients was 56.6 (SD 17.7) years. 269 cases could be histologically classified and included in the study. In all, 222 (82.5%) were located on feet. According to melanoma subtype, 165 (61.3%) were acral lentiginous melanoma (ALM), 84 (31.2%) were superficial spreading melanoma (SSM), and 20 (7.5%) were nodular melanoma (NM). SSM patients were characterized by female predominance (77.4%), younger age, and classic melanoma-risk phenotype (fair skin and multiple nevi). Among the 198 invasive cases with a mean follow-up of 56.2 months, the mean (SD) Breslow’s thickness was 3.1 (3.6) mm, being 1.4 (1.4) mm in SSM, 3.5 (4.1) mm in ALM and 4.9 (2.9) mm in NM (P<0.001). Ulceration was present in 33.3%, 2.9% in SSM, 38.6% in ALM, and 76.9% in NM (P<0.001). A total of 29.3% relapsed (7.3% of SSM, 35% of ALM and 55% of NM) and 24.2% died because of AM. In multivariate analysis, age at diagnosis, Breslow, and histopathological subtype were independent prognostic factors for both disease-free and AM-specific survival. The ALM and NM subtypes presented poorer outcome after weighting Breslow and age (P=0.02). Histological subtype of AM could have an impact on biological behavior, ALM and NM subtypes presenting a poorer prognosis after adjusting for age and Breslow’s thickness.