A non-healing ulcerated fingertip following injury

Nail pigmentation

The 2 most important signs of subungual melanoma are melanonychia striata (longitudinal brown to black pigmented streaks in the nail) and Hutchinson’s sign, which is the spread of brown or black pigment from the nail bed, nail matrix, or nail plate onto the adjacent cuticle or onto the proximal or the lateral nail fold.

Many patients with subungual melanoma have a history of a thin pigmented streak that had remained unchanged for years and then suddenly began to enlarge—eventually involving the entire nail bed with subsequent penetration to the eponychium or paronychium, ulceration, or granuloma formation.

Melanonychia striata. The differential diagnosis of melanonychia striata is quite long, and most of these streaks are benign (TABLE 2). Dark brown or black lines in the nails are common in Asians, African Americans, and in dark-skinned individuals, and may simply represent ethnic variation in pigment. Multiple streaks and streaks that do not extend distally from the proximal nail fold are nearly always benign.

Single streaks greater than 6 mm wide, those appearing in the sixth and seventh decade of life, streaks with a variegated color, or those that exhibit a broader proximal base or undergo any morphological change (indicating an active process) are suspicious for subungual melanoma.

Hutchinson’s sign. Hutchinson’s sign is pathognomonic for subungual melanoma only when accompanied by ulceration of the nail bed or obliteration of the nail plate by granuloma. When present, a tissue diagnosis must always be sought.

TABLE 2
Common differential diagnoses of multiple pigmented nail streaks or periungual pigmentation