Subungual melanoma: a study of 124 cases highlighting features of early lesions, potential pitfalls in diagnosis, and guidelines for histologic reporting.

Department of Anatomical Pathology, Royal Prince Alfred Hospital, Camperdown, Australia.
American Journal of Surgical Pathology (Impact Factor: 4.59). 01/2008; 31(12):1902-12. DOI: 10.1097/PAS.0b013e318073c600
Source: PubMed

ABSTRACT Subungual melanoma (SUM) is an uncommon variant of melanoma that is often difficult to diagnose, both clinically and pathologically. In an attempt to provide pathologic clues to diagnosis, especially in early lesions or small biopsies, and to provide practical advice to pathologists in reporting, the clinicopathologic features of 124 cases of SUM were reviewed, the largest series reported to date. The features of 28 cases of subungual melanoma in situ (MIS), comprising 4 cases of MIS and 24 cases where areas of MIS were present adjacent to dermal-invasive SUMs, were compared with those of a similar number of acral nevi to identify useful distinguishing features. The median age of the patients was 59 years and the most common site was the great toe (24%). Nine percent of cases were AJCC stage 0, 14% were stage I, 41% were stage II, 32% were stage III, and 4% were stage IV at initial diagnosis. The commonest histogenetic subtype was acral lentiginous (66%), followed by nodular (25%) and desmoplastic (7%). The majority of tumors were locally advanced at presentation with 79% being Clark level IV or V. The median Breslow thickness was 3.2 mm. The median mitotic rate was 3 per mm and 33% of cases demonstrated primary tumor ulceration. Seven of 29 patients (24%) who underwent a sentinel lymph node biopsy had nodal disease. Multivariate Cox-regression analysis showed higher disease stage to be the only significant predictor of shortened survival. In comparison to acral nevi, MIS more frequently showed lack of circumscription, a prominent lentiginous growth pattern, predominance of single cells over nests, moderate-to-severe cytologic atypia, a dense and haphazard pagetoid intraepidermal spread of melanocytes, and the presence of junctional/subjunctional lymphocytes ("tumor infiltrating lymphocytes"). Tumor infiltrating lymphocytes have not been highlighted previously as a feature of subungual MIS and represent a useful diagnostic clue. Guidelines for the reporting of SUMs are also presented. Knowledge and recognition of the pathologic features of SUMs and the important features that distinguish them from nevi should reduce the frequency of misdiagnosis.

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    Annals of Dermatology 10/2014; 26(5):655-7. DOI:10.5021/ad.2014.26.5.655 · 0.95 Impact Factor
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    ABSTRACT: Subungual melanoma (SUM) is rare and represents approximately 2–3% and 20% of all cutaneous melanomas in Caucasians and Asians, respectively. Amputation has usually been performed for invasive SUM; however, not all invasive SUMs invade or attach to the distal phalanx. To investigate the possibility of non-amputative surgery for patients with invasive SUM, the distances between the deepest base of the melanoma cells and the bony surface in the surgical specimens of invasive SUM were measured. Thirty surgical specimens of invasive SUM were retrospectively reviewed. The contents of the specimens were as follows: 14 first toes, 10 thumbs, three second fingers, two third fingers, and one fifth finger. Four specimens showed bone invasion, and the tumor was attached to the bone in four specimens. The tumor-to-bone distance exceeded 0.9 mm in all the specimens with thicknesses <4 mm. In the non-ulcerated SUMs (nine specimens), only one SUM specimen showed bone attachment. There was a higher likelihood of bone attachment or invasion when tumor thickness (TT) exceeded 4 mm (Pearson chi-square test, P = 0.009; Fisher exact test, P = 0.004; student t test, 0.033). Univariate and multivariate analysis also revealed that thick TT had a statistically significant affect (odds ratio 1.807 and 1.865, 95% CI 1.11–3.01 and 1.11–3.13, P = 0.023 and 0.018). Non-amputative surgery may be possible for SUM tumors that are of intermediate-thickness. However, there has been little evidence demonstrating survival with non-amputative surgery for invasive SUM. A large, randomized, prospective clinical study is required to address this issue.
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