Can You Identify This Nail Lesion?

A 54-year-old Caucasian man presents with more than a 9 month history of a dark band on the right fifth finger. The patient denies any history of trauma and reports that the dark band has not increased in size or become darker. On exam, no dark band was observed on other digits.

What are you looking at here?

(Answer and discussion on next page)

Answer: Acral melanoma in situ

The differential diagnoses for this case include acral melanoma versus benign melanocytic nevi. Isolated pigmentation on a single digit, especially in individuals over the age of 40s, should prompt high suspicion for malignant melanoma.

Dermoscopic exam of the lesion showed multi-colored (ie, black, dark brown, and light brown) bands with irregular thickness and space between the bands. The pigmentation extended through the full length of the nail (Figure 2). Close inspection also showed Hutchinson’s sign, the presence of brown pigmentation on the proximal nail fold.

The lesion was biopsied; the pathology report showed melanoma in situ.