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.