Acral lentiginous melanoma: conventional histology vs. three-dimensional histology

Patients with acral lentiginous melanoma (ALM) seem to have a poor prognosis. ALMs represent 4-10% of cutaneous melanomas in white populations. Surgery is mostly based on conventional histological evaluation. With micrographic surgery, continuously spreading tumours can be excised with smaller excision margins for better cosmesis and function.

Clinical parameters and surgical strategies influencing the prognosis of patients with ALM were evaluated.

Two hundred and forty-one patients (44% male, 56% female) with stage I/II ALM were recorded during 1980-2006. One hundred and thirty-three patients underwent complete histology of three-dimensional excision margins (3D histology) using the paraffin technique. Risk factors for disease-specific and recurrence-free survival were estimated.

Patients were aged 26-87 years (median 63) with median tumour thickness of 2.0 mm. The median follow-up was 41 months. Multivariate analysis identified ulceration, conventional histology and tumour thickness as risk factors for recurrence-free and disease-specific survival. Using 3D histology, excision margins were significantly smaller (median 7 vs. 20 mm) without an increased risk of local recurrences. Patients with 3D histology had a 5-year survival of 81% compared with 63% with conventional histology. Retrospective analysis with immunohistological methods (anti-Melan-A) could improve the diagnostic specificity in detecting further melanocytic cell nests.

Clinical and surgical risk factors seem to have different influences on the outcome of ALM. 3D histology allows reduction of excision margins by two-thirds without an increased risk of local recurrences and with better prognosis. 3D immunohistology could be a valuable diagnostic tool to reduce the rate of local recurrences.