A case of acral melanocytic hyperplasia: a unique pigmented lesion mimicking acral lentiginous melanoma in situ

Early detection of acral melanoma: A review of clinical, dermoscopic, histopathologic, and molecular characteristics

Acral lentiginous melanoma is a distinct subtype of melanoma on acral skin. Patient presentation at later stages and delayed diagnosis by physicians contribute to a worse associated prognosis and survival rate. Despite our progress in understanding the key features of this disease, the diagnosis of early-stage acral melanoma is still challenging. It is essential to integrate clinical, dermoscopic, and histologic findings in the diagnosis of acral lentiginous melanoma. In addition, molecular studies can be helpful. In this review, we have summarized our current understanding of this disease entity from articles that were published between 1969 and 2018. We have outlined clinical and dermoscopic features as well as pathologic and molecular findings regarding acral melanoma and have presented an algorithm for diagnosis. Understanding and integrating these characteristics may assist clinicians in the early detection of acral melanomas.

Acral Lentiginous Melanoma Developing during Long-standing Atypical Melanosis: Usefulness of Dermoscopy for Detection of Early Acral Melanoma

Clinical guidelines suggest that suspicious pigmented lesions of the plantar or palmar area require biopsy for early detection of acral melanoma. We present here a case of acral lentiginous melanoma in which various melanocytic atypia was observed at each biopsy site, including focal melanocytic proliferation. We suggest that this atypical melanosis is part of a contiguous phase of invasive tumor growth, which is known as the very early stage of melanoma in situ. In addition, noninvasive dermoscopy has been effective for the early discovery of hidden lesions of acral melanoma.

Early Acral Melanoma In Situ

In non-white populations, acral skin is the most prevalent site of malignant melanoma. Early melanomas of this anatomic site are often misdiagnosed as melanocytic nevi, which are not uncommon on acral skin. In fact, clinical and/or histopathological features of melanocytic nevi occasionally mimic those of early acral melanoma and vice versa, and thus differentiation of early acral melanoma from melanocytic nevus is sometimes very difficult for clinicians as well as for histopathologists. Our dermoscopic investigation has revealed that the parallel ridge pattern, a band-like pigmentation on the ridges of the skin markings, is highly specific to malignant melanoma in situ on acral volar skin. In the present study, we reviewed 22 acral melanocytic lesions that showed the parallel ridge pattern on dermoscopy but had very subtle clinical and/or histopathological presentations. We diagnosed 20 of them as early melanoma in situ by careful histopathological examination, which revealed histopathological features very similar to those seen in macular portions of overt acral melanoma, but fundamentally different from features found in melanocytic nevi on acral skin. In correspondence with their dermoscopic pattern, in these early lesions of acral melanomas, proliferation of solitary arranged melanocytes was mainly detected in the crista profunda intermedia, the epidermal rete ridge underlying the ridge of the skin marking. The two remaining lesions were diagnosed as possible cases of acquired melanocytic nevus because of the formation of well-demarcated nests of melanocytes in the epidermal rete ridges. We propose that a finding of preferential proliferation of solitary arranged melanocytes in the crista profunda intermedia is an important clue for the histopathological diagnosis of early phases of acral melanoma.

The characteristic histopathologic features of nevi on and around the ear

BACKGROUND

Nevi on certain areas of the body such as the acral, genital, and flexural regions may exhibit uncommon but characteristic histopathologic features. The purpose of this study was to characterize the distinctive features of nevi with a junctional component located on and around the ear.

MATERIALS AND METHODS

A total of 101 compound and junctional nevi of the ear received at the Yale Dermatopathology Laboratory during a 10-year period were examined in this study. The most characteristic feature of the majority of these nevi was irregularity of nesting pattern, with nests, which varied in size and shape and which were sometimes located between rete ridges.

RESULTS

Forty-two (42%) of nevi on and around the ear showed poor circumscription, lateral extension of the junctional component beyond the dermal component, and elongation of rete ridges with bridging between them. A subset of these nevi (26 cases) showed uniformly large melanocytes with large vesicular nuclei without prominent nucleoli, and abundant pale, finely granular cytoplasm. These lesions did not show a tendency to recur.

CONCLUSIONS

This study supports the existence of a subset of nevi on or near the ear that, like certain nevi located on other special sites, exhibit unusual but characteristic features, which may be misinterpreted as atypical or malignant.

Acral Lentiginous Melanoma In Situ: A Study of Nine Cases

An acral lentiginous melanoma (ALM) is the most common type of cutaneous melanoma in Asians. However, it is unusual to encounter a patient showing only the histologic features of an ALM in situ. Here we describe clinical and histologic features of nine cases of ALM in situ including immunohistochemical staining with anti-S100 protein and HMB-45. All the patients had a long clinical history. Clinically, the lesions were characterized by a longitudinal pigmented streak in the nail plates, black pigmentation on the proximal or lateral nail fold, and an irregular border and variegated pigmentation on the sole or thumb. Total resections of the lesions were performed in all patients. All lesions, in both biopsy and excisional specimens demonstrated more melanocytes generally located in the basal layer of the epidermis. There was no dermal invasion. No recurrence of the disease had occurred in any patient after a follow-up period of between 6 months to 12 years after surgery. These results suggest that ALM can evolve slowly over many years.

Superficial spreading melanoma arising in a longstanding melanocytic nevus on the sole

In Asians, the plantar surface is the commonest site for cutaneous melanoma, and most melanomas arising in this region are the acral lentiginous type. Herein we describe a rare case of superficial spreading melanoma arising in a longstanding melanocytic nevus on the sole of a Korean.