In situ nail unit melanoma: epidemiological and clinic‐pathologic features with conservative treatment and long‐term follow‐up

Background Nail unit melanoma (NUM) is a rare melanoma variant, usually associated with a poor prognosis because of a delayed diagnosis. Few data are available concerning the management and long‐term outcome of in situ NUM. Objective To use a large cohort to provide comprehensive patient data and long‐term follow‐up information. This will serve to investigate distinctive epidemiological, clinical and histological features of in situ NUM. To report treatment modalities, assess conservative surgery and evaluate its long‐term safety. Methods Patients with confirmed diagnosis of in situ NUM were retrospectively reviewed. Demographics, clinical presentation, therapeutic data and follow‐up were analysed. Results Sixty‐three cases of in situ NUM were identified as follows: 44 were women (70%), with a mean age of 51 years. The mean duration of symptoms prior to consultation was 4.3 years [range 3 months–28 years]. Clinically, with 58 cases, i.e. (92%) longitudinal melanonychia was the most common clinical presentation. The thumb was the most affected digit, being afflicted in 28 cases: 44%. Medical history found a widening and/or recent darkening of the melanonychia in 46 cases (82%). The treatment consisted of, respectively, 56 En bloc excisions of the nail apparatus 89% of the patients we studied, and seven amputations of the distal phalanx. During the follow‐up period (mean: 10 years), two patients presented in situ recurrences. Conclusion The recognition of a NUM at an in situ stage allows early treatment and curing of this tumour. At this early stage, a ‘functional surgery’ is a rational approach with an excellent oncologic safety.