Melanoma of the proximal nail fold mimicking Hutchinson sign.

Clinical presentation

We present the case of a 32-year-old Asian woman who reported the onset of a pigmented lesion on the proximal nail fold of the third finger of her left hand approximately 6 months ago. She had not noticed any pronounced enlargement or other symptoms since then. On clinical examination, a dark-brown, elongated, well-demarcated lesion was observed on the proximal nail fold of the third finger of the left hand, which did not affect the adjacent nail (Fig 1).

Fig 1

Clinical image showing a dark-brown, elongated, well-demarcated macule on the proximal nail fold of the third finger of the left hand. The lesion does not affect the adjacent nail plate.

Dermoscopic appearance

A dermoscopic examination of the lesion revealed structureless areas and different shades of color, including brown and nearly black, as well as some brownish globules and streaks (Fig 2). A total excision of the pigmented lesion was performed.

Fig 2

Dermoscopic examination revealed different colors, including shades of brown and nearly black, as well as some dark-brown globules and streaks.

Histologic diagnosis

The histopathologic examination revealed an increased number of melanocytes predominantly located at the dermoepidermal junction. The cytomorphologic investigation showed mostly nevoid and dendritic pigmented melanocytes (Fig 3). The lesion was diagnosed as cutaneous melanoma in situ.

Fig 3

Histopathologic image of the lesion, showing an increased number of melanocytes predominantly located at the dermoepidermal junction. Anatomic absence of the lesion to the nail apparatus is apparent.

Hutchinson sign, which was first described in 1886 by Jonathan Hutchinson, is defined as a periungual, brownish-black area of pigmentation that originates from the nail bed and nail matrix and subsequently involves the surrounding skin. It is a worrisome sign because it typically occurs in advanced stages of nail melanomas. The so-called micro-Hutchinson sign, however, is a true pigmentation of the cuticle and can be observed only with dermoscopy. It implies the presence and progression of nail melanomas.

Our case is striking because the lesion on the proximal nail fold resembled Hutchinson sign, but no nail pigmentation or infiltration of the nail matrix was observed. Furthermore, the histologic examination revealed melanocytes only in the epidermis. Thus, the lesion was diagnosed as a primary cutaneous melanoma in situ.1, 2, 3, 4