Review Question - QID 217358

This patient demonstrates Hutchinson's Sign, a clinical exam finding associated with subungual melanoma. A full-thickness biopsy is required to evaluate for melanoma.

Melanoma is a malignancy derived from melanocytes and characterized by brown-black pigmented lesions in the skin. They develop most often in sun exposed areas and can develop under nails, most often of the thumb. When involving the nail bed or plate, they can grow in line with the nail longitudinal growth making the characteristic finding known as Hutchinson's sign. Diagnostic work-up should include nail plate removal and full-thickness biopsy to identify signs of malignancy and depth of involvement. The standard of care for subungual melanoma is amputation with sufficient margins (1-2cm). Nevi, subungual hematomas, and onychomycosis can all present very similar to subungual melanoma and should be excluded.

Baran et al. published an extensive list of non-melanoma conditions that can present with Hutchinson's sign. These include ethnic pigmentation, onychomatricoma, onychomycosis, Laugier syndrome, and nevi. They conclude by cautioning the presence of Hutchinson's sign is not a definitive diagnosis of melanoma and further workup is required when present.

Drs. Littleton, Murray, and Baratz published a review on the evaluation, biopsy, treatment, and long-term survival in patients with subungual melanoma. They recommend a biopsy when longitudinal melanonychia is present in a single-digit or if there is a change in the appearance of previously stable melanonychia. Biopsy should involve nail plate removal, opening of the eponychial fold, and full-thickness down to the underlying periosteum.

Figure A shows Hutchinson's sign, a periungual extension of brown-black pigment from the nail bed and nail matrix onto the surrounding tissues.

Incorrect Answers:
Answer 1-3: This patient has a single-digit melanonychia and should undergo a biopsy to rule out melanoma instead of conservative treatment or other treatment options once a different etiology is determined.
Answer 4: Disarticulation through the IPJ would likely be his definitive treatment once subungual melanoma is diagnosed via a biopsy.