Melanonychia: diagnosis and treatment

Melanonychia should be a term restricted to the presence of melanin in the nail unit. To be able to understand the process of melanin deposition in the nail plate, the nail apparatus and its melanocyte system are described. The different causes responsible for a black nail are reviewed, enabling the clinician to pick out those cases that are highly suspicious of being a malignant condition. Their differential diagnosis is also considered, with special attention to Hutchinson's sign. The second part of the article deals with the management of longitudinal melanonychia, including history, clinical examination, nail plate sampling, and when and how to perform a biopsy. Finally, pathology and subungual melanoma treatment are briefly reviewed.     

Subungual melanoma: Histological examination of 50 cases from early stage to bone invasion

Subungual melanoma is a rare form of malignant melanoma. It is extremely difficult to differentiate it histologically from benign melanonychia striata or melanocytic nevus, especially in the early stage. We divided 50 cases of subungual melanoma into four groups according to clinical progress, and examined their histological findings in each respective stage. In the early stage (19 cases), atypical melanocytes were polygonal showing slight nuclear atypia with no mitoses at all. In six out of 19 cases (31.6%), the atypical melanocytes proliferated more in the hyponychium than in the nail matrix, and only very few in the nail bed. Periungual pigmentation (Hutchinson's sign) appeared from the early stage in almost all cases. With stage progression (middle stage, 13 cases; progressive stage, 13 cases; and bone invasive stage, five cases) the number of atypical melanocytes and their degree of nuclear atypia increased, and the ascent of atypical melanocytes and pagetoid spread became conspicuous. Mitoses became apparent only from the progressive stage. From these observations, we would like to propose three new pathological clues of early stage subungual melanoma: (i) “skip lesion”, proliferation of the tumor cells are more prominent in the hyponychium than in the nail bed or nail matrix; (ii) histological confirmation of Hutchinson's sign; and (iii) epithelial thickening and/or compact arrangement of the elongated basal cells.     

Early malignant melanoma manifested as longitudinal melanonychia: subungual melanoma may arise from suprabasal melanocytes

A 51-year-old woman developed longitudinal melanonychia of 3 months' duration on the right index fingernail. A biopsy specimen revealed that atypical melanocytes were distributed in the lower third of the matrix epithelium but were few in number at the basal layer. The involved nail matrix was resected because of continual growth of the lesion after the biopsy. It has been proven in normal nail matrices that melanocytes are distributed not only in the basal layer but also in the lower half of the epithelium. It is therefore understandable that malignant melanoma of the nail matrix can arise from melanocytes situated in the squamous epithelium above the basal layer. The present case is a good example in which malignant melanoma of the nail matrix may arise from the intraepithelial region where melanocytes normally reside.     

Clinical and dermoscopic features of nail unit melanoma in an Australian nail clinic cohort

Nail unit melanoma carries diagnostic challenges conferring with its poor prognosis. This audit aims to characterise both clinical and dermoscopic features of nail unit malignant lesions and compare them with biopsied benign lesions. It focuses on informing future practice by aiding in the stratification and recognition of malignant diagnostic patterns in the Australian context.     

Acral cutaneous melanoma in caucasians: clinical features, histopathology and prognosis in 112 patients

BACKGROUND: Acral lentiginous melanoma (ALM) is the fourth distinct variant of cutaneous melanoma. The histological diagnosis and prognosis of ALM are still controversial. OBJECTIVES: To review the features of a large series of patients with ALM, and confirm the validity of the histological criteria for this type of melanoma. METHODS: A collection of 2642 patients with cutaneous melanoma was recorded during the period 1986-97, among these 187 were located on acral sites. Histological specimens were reviewed in 112 acral melanomas; the following study is based on this subgroup. RESULTS: Histological examination revealed acral lentiginous melanomas predominantly in palmoplantar and subungual locations (60%), while superficial spreading melanomas (SSM) were found mainly on the dorsal aspects of hands and feet (30%). Nodular melanomas (NM) (9%) occurred in all acral sites. The histological re-examination confirmed the characteristics of ALM as described by Reed in 1976. With increasing tumour thickness nesting of tumour cells and upward migration to the cornified layer was similarly observed. The 5-year survival rate for patients with primary acral melanoma without recognizable metastasis was 82%. ALM differed significantly in survival from SSM (P = 0.001) and lentigo maligna melanoma (P < 0. 001), but survival rates were similar to NM (P = 0.9). CONCLUSIONS: ALM, as diagnosed by current histological criteria, occur on the palms, soles and subungual sites, and have a poor prognosis.     

Acral lentiginous melanoma: histopathological prognostic features of 121 cases

BACKGROUND: Acral lentiginous melanoma (ALM) is the fourth histopathological subtype of malignant melanoma, accounting for < 10% of all melanomas in white-skinned populations. It is characterized by a lentiginous pattern of proliferation of the intraepidermal component of the tumour. Its individualization is still controversial, especially in regard of its prognostic value. OBJECTIVES: To characterize better ALM from a pathological point of view and to assess the prognostic value of all histopathological features of ALM. METHODS: We performed a review of all cases of ALM followed from 1996 to 2004 at the University Hospital Department of Dermatology, Lyon, France. We examined all haematoxylin, eosin and saffron-stained tissue sections of the primary lesions. Several pathological parameters of interest in melanoma were evaluated for disease-free and specific survival with the Kaplan-Meier method and the Cox proportional hazards regression model. RESULTS: Representative histological material was available for 121 patients. The mean Breslow thickness was 2.5 mm (in situ-20 mm). Fifteen lesions (12%) were in situ, nine (7%) were at Clark level II, 35 (29%) at III, 40 (33%) IV and 22 (18%) V. Extension along adnexal structures was found in almost half of the ALMs (46%), without prognostic significance. Seventeen (14%) lesions showed no microscopic pigmentation. Remnants of pre-existing naevus were found in four (3%) melanomas. The width of the 36 (30%) ulcerated lesions ranged from 1 to 20 mm (mean 7.6). Ulceration and its width were both associated with a large tumour thickness (P < 0.01), a high level of invasion (P < 0.01), the presence of vascular invasion (P < 0.01) and the lack of pigment production (P < 0.01). Among the 99 ALMs which were in the vertical growth phase (VGP), 21 showed a high mitotic rate (> 6 mitoses mm(-2)). A high mitotic rate was found to be significantly associated with the presence of ulceration (P < 0.01). The presence of microscopic satellites was noted in 10 (10%) lesions. The uncommon presence of small cells (8%) in the VGP was statistically significantly (P < 0.01) associated with a worse prognosis compared with other cell types. Multivariate analysis identified mitotic rate (P < 0.01), microsatellites (P = 0.05), Clark level (P = 0.01) and gender (P = 0.03) as independent prognostic factors for disease-free survival. Only the presence of microsatellites (P = 0.02) and a high mitotic rate (P < 0.01) were independently correlated with specific survival in ALM. CONCLUSIONS: This is a detailed pathological study of a large cohort with ALM, an uncommon subtype of melanoma. Mitotic activity appears to be of particular importance in predicting the outcome of ALM.