Melanoma of thumb: retrospective study for amputation levels, surgical margin and reconstruction

For the treatment of melanoma of thumb, the evidence about amputation level (IP joint or MP joint) and cutaneous excision margin has not been fully presented. And reconstructions for lost thumbs need to be balanced against functional and aesthetic requirements of individual patients and overall prognosis. We report 15 patients, who underwent primary excision and reconstruction for thumb melanoma between 1986 and 2004 at Department of Plastic and Reconstructive Surgery, University of Hokkaido at Sapporo, Graduate School of Medicine. The patients were reviewed to evaluate the prognostic significance of variables including age and sex of the patient, tumour thickness, staging, level of amputation, and cutaneous excision margin. Our 15 cases were divided into two groups according to amputation level (MP or IP) and cutaneous excision margin (<40 mm or >or =40 mm) and prognosis was analysed statistically. The stage and thickness were identified as prognostic factors for disease-free survival; however, IP amputation and 10-30 mm margin did not compromise disease-free survival. Amputated thumb was reconstructed by pollicization, free toe to thumb transfer, reverse forearm flap, local flap, and skin graft. No major complication of reconstructed thumb occurred. Seven of eight cases of MP amputation were reconstructed by pollicization. On the other hand, five cases of IP amputation were reconstructed by volar skin flap in two cases, reverse forearm flap in two cases, and trimmed first toe transfer in one case. Although a small number of cases, our study is the first attempt focussing on melanoma of thumb, and evaluating amputation level and cutaneous margin separately. The reconstructive algorithm for the amputated thumb is proposed and has various tools including free toe to thumb transfer.