Background: Melanonychia of the digit is uncommon in the Caucasian population and is concerning because of potential malignant transformation. Several histologic changes occur before malignant transformation, including melanocytic atypia. The authors evaluated patients with melanonychia with melanocytic hyperplasia to determine the risk factors for malignant transformation.
Methods: The authors retrospectively reviewed records for patients older than 18 years that underwent biopsy for melanonychia. They identified 22 patients with melanocytic hyperplasia with a median age of 61 years (interquartile range, 44 to 71 years). A bivariate analysis was performed to evaluate whether the degree of atypia was associated with malignant transformation and whether treatment choices by surgeons were based on melanocytic atypia.
Results: Following biopsy, patients were followed for a median of 41.0 months (interquartile range, 4.8 to 100.6 months). Melanocytic atypia was present in nine patients and transformed into a malignancy in three: in two patients it became a melanoma in situ, and in one it became an acral lentiginous melanoma. Moderate-severe and severe melanocytic atypia was associated with malignant transformation. After initial biopsy, 14 patients were monitored (11 without atypia and three with atypia). One patient with slight atypia, two patients with moderate-severe atypia, and two patients with severe atypia underwent additional treatment. Patients with melanocytic hyperplasia without atypia were monitored more often (78.6 percent versus 21.4 percent).
Conclusions: Melanonychia presents a challenge to the hand surgeon, as some patients may be monitored and some should undergo additional resection. Patients with moderate-severe melanocytic atypia following biopsy should undergo resection, and those with mild to slight atypia can most often be monitored clinically.
Clinical question/level of evidence: Therapeutic, IV.