Extrafacial Lentigo Maligna: A Report on 14 Cases and a Review of the Literature

Clinical and histopathological features of lentigo maligna and lentigo maligna melanoma: a retrospective analysis in Korea

Introduction

Lentigo maligna (LM) and lentigo maligna melanoma (LMM) are rare in Asian countries. The histopathological diagnosis of LM is often challenging, and misdiagnosis is common. Although histopathologic features of LM/LMM are known, statistical analysis of them were scarcely reported. In this study, we aimed to investigate the histopathological characteristics of LM/LMM in Korean patients and identify key histopathological clues distinguishing LM from benign lentigo.

Methods

We performed a retrospective study of the clinical and histopathological features of patients diagnosed with LM/LMM at our center between 2011 and 2022. We assessed the histopathological features in each case based on 16 pathological criteria according to previous literature. Pathologically confirmed cases of benign lentigo were analyzed for comparison.

Results

Twenty-one patients (10 with LM and 11 with LMM) were analyzed. Several statistically significant difference existed between the features of LM and benign lentigo (N = 10), including asymmetry of overall structure (p < 0.001), cytologic atypia (p < 0.001), predominant single-cell proliferation (p < 0.001), melanocytic nests (p = 0.033), melanocytes forming rows (p = 0.003), pagetoid spread of melanocytes (p < 0.001), and hair follicle invasion by atypical melanocytes (p < 0.001). Degree of solar elastosis was more severe in group "Age ≥ 60" (p = 0.015), and group "Diameter ≥ 20 mm" (p = 0.043). Presence of elongated rete ridges were less common in the older than 60 age group (p = 0.015) and group "Diameter ≥ 20 mm." Invasion was associated with mitosis (p = 0.001, OR 49.285), multinucleated cells (p = 0.035, OR 17.769), and degree of lymphocyte infiltration (p = 0.004).

Conclusion

This study investigated the clinical and histopathologic characteristics of LM and LMM in Koreans. Although histopathological diagnosis is challenging, especially in the early stages of LM, our data showed essential histopathological changes in architectural, cytological, and dermal patterns. Considering the potential aggressiveness of LM/LMM, it is essential to recognize its histopathological features and provide timely management.

Diagnosis and Management of Lentigo Maligna: Clinical Presentation and Comprehensive Review

Lentigo maligna (LM), also known as Hutchinson's melanotic freckle, is a form of in situ melanoma characterized by the proliferation of atypical melanocytes along the basal epidermis in sun-damaged skin. If left untreated, LM will progress to lentigo maligna melanoma (LMM), a form of invasive melanoma with the same prognosis as other forms of invasive melanoma. LM is more common in the elderly, with a peak occurrence between the ages of 65 and 80 years. LM, however, is rarely present on the trunk and extremities. The diagnosis of LM, confirmed by histopathological and biopsy examination, is based on clinical and dermoscopic features. It typically begins as a tan-brown macule or patch, but it can progress to a variegated pigmentation with dark black color or even amelanotic characteristics. The risk factors involved in the LM development include a history of sunburns, lighter skin types, advanced age, history of nonmelanoma skin cancers, and tendency to form solar lentigines. This article explains the clinical presentation of LM, also reviews the available information on the diagnosis and management of LM, and discusses the potential of such information in facilitating the future prospective.

Lentigo Maligna: Clinical Presentation and Appropriate Management

Lentigo maligna (LM) is a type of melanoma in situ that has distinctive characteristics regarding epidemiology, risk factors and clinical features. In addition, LM has a potential to progress to an invasive tumor with potentially aggressive behavior: lentigo maligna melanoma (LMM). Overall, LM has a very good prognosis, whereas LMM has the same prognosis as other invasive melanomas with similar Breslow thickness. LM/LMM represents a challenging entity not only regarding the diagnosis but also regarding the management. Diagnostic criteria are not well established, and there is an overlap of clinical, dermoscopic and pathological features with other benign pigmented skin lesions such as lentigines, pigmented actinic keratoses or macular seborrheic keratoses. LM/LMM's common appearance within photodamaged skin makes lesion border identification difficult. Wide excisions are often required, but since LM/LMM typically appears on cosmetically sensitive areas such as the face, sometimes large excisions are not possible nor desirable. In this sense, specialized approaches have been developed such as margin-controlled surgery or image-guided treatment using reflectance confocal microscopy. Other treatments for LM such as cryosurgery, imiquimod, radiotherapy or photodynamic therapy have been proposed, although recurrence/persistence is common. The current manuscript reviews extensively the published data regarding the diagnosis, treatment and management of both complex entities LM and LMM.

Key dermoscopic signs in the diagnosis and progression of extrafacial lentigo maligna: Evaluation of a series of 41 cases

BACKGROUND/OBJECTIVES

Lentigo maligna is usually located on the face. Extrafacial lentigo maligna is less common, and diagnosis of early forms is very difficult. Confocal microscopy of facial and extrafacial lentigo maligna shares the same features (abundant dendritic cells and generalised atypical junctional thickenings) and helps us to identify the dermoscopic features of extrafacial lentigo maligna.

METHODS

We analysed dermoscopic and clinical features of 41 lesions diagnosed by confocal microscopy of extrafacial lentigo maligna confirmed on histology to identify dermoscopic signs of early lesions.

RESULTS

Erased areas on dermoscopy were the clue to diagnose early lesions. At the borders of these areas, very small, round or triangular structures were found. At the lesion periphery, dermoscopy revealed a fine reticular pattern that helped to identify them as a melanocytic lesion. A progressive increase of the number and size of erased areas was accompanied by the appearance of various angulated structures around them (angulated lines, zig-zag structures or polygonal structures). Analysis of invasive lesions revealed very large erased areas containing white lines and atypical vascularisation.

CONCLUSIONS

We have identified the dermoscopic early features and signs of progression by examining the dermoscopic and reflectance confocal microscopy findings of early and invasive extrafacial lentigo maligna.

Lentigo Maligna - Not Always a Face and Neck Disease of the Elderly

INTRODUCTION

Lentigo maligna (LM) is a rare form of in situ melanoma, frequently seen as a large patch in elderly patients. The aim of this study was to assess clinical and dermoscopic features of LM.

MATERIAL AND METHODS

A retrospective study of LM patients presenting to our center between July 2007 and July 2017 was performed. Demographic data, anatomical location, laterality, diameter, Clark level, Breslow stage, "ABCD" signs and dermoscopic features were registered. Facial versus extrafacial LM were compared.

RESULTS

We found 21 LM, of which 12 had an extrafacial location and 9 a facial location. Half of the extrafacial lesions were located on an upper limb. The median age at diagnosis was 63 years (ranging from 38 to 84 years). Most LM cases were female (16/21) with phototype II (13/21). More than half of the patients (11/21) had a history of a skin neoplasm or actinic keratosis. The median diameter found was 6 mm (interquartile range = 4.5 mm), ranging from 1 to 15 mm. Five lesions were invasive (median Breslow depth of 0.2 mm), and 4 of them were extrafacial.

DISCUSSION

In this study LM was more frequently found in an extrafacial location and as a small patch with a 6-mm diameter medium. The epidemiology of LM/LM melanoma might be changing. Full body examination and dermoscopy are of the utmost importance for the diagnosis. Dermatologists should be aware and search for small lesions outside the face and neck, particularly in middle-aged female patients with photo-damaged skin.