A review of nevus-associated melanoma: What is the evidence?

Cutaneous melanoma may have an adjacent nevus remnant on histological examination in 30% of cases (nevus-associated melanoma, NAM), while it may appear de novo, without a precursor lesion, in the remaining 70% of cases. Nevus-associated melanoma and the concept of acquired melanocytic nevi serving as precursors of melanoma, has long been considered as a controversial topic. This controversy is, in part, due to their overall low rate of transformation to melanoma and scarce data on the natural history of progression. Another matter of debate regarded the possibility that the reported differences of NAM versus de novo melanoma, were due to an underestimation of NAM in thicker lesions due to obliteration of the nevus component by the tumour. During the last few years, several evidence has accumulated in order to address these controversies. In this review, we present a comprehensive synthesis of the epidemiological, clinical, dermoscopic and genetic findings in NAM, including thin NAM, compared to de novo melanoma. Answering the questions on nevus-associated melanoma may provide further insight on the classification of these tumours and disentangle their biology and route of development from that of de novo melanoma.

Dermoscopy of congenital melanocytic nevi: a ten-year follow-up study and comparative analysis with acquired melanocytic nevi arising in prepubertal age

Dermoscopic characteristics of congenital melanocytic nevi (CMN) have been reported, however, dermoscopic variation during long-term follow-up and direct comparative analyses with acquired melanocytic nevi (AMN) are poorly documented. To assess dermoscopic changes of CMN (including lesions present at birth or appearing within the first two years of age) after a long-term period and evaluate possible dermoscopic differences with AMN arising during prepubertal age. We re-analysed clinical and dermoscopic features of CMN, investigated ten years earlier. New findings were compared with those previously recorded, as well as with those of AMN appearing before puberty in the same group of patients. In total, 493 lesions (86 CMN and 407 AMN) from 71 patients were examined. Except for a greater size (median area: 73.9 vs 22.8 mm²; p<0.001) and higher prevalence of hair (17.4% vs 4.7; p<0.001) in CMN, no significant difference was observed between the two cohorts, including global/local dermoscopic features (p>0.05). The follow-up of CMN revealed that dermoscopic pattern changed in only four lesions (4.7%) (from globular to globular-reticular or reticular) after ten years, though lesions with a globular architecture presented several "local" changes, namely an increase in circumscribed reticular areas (from 20.0% to 41.5%; p = 0.030), irregularly distributed globules (from 15.6% to 34.1%; p = 0.045), and large globules (from 46.7% to 68.3%; p = 0.043). The dermoscopic appearance of CMN is significantly stable during childhood and is similar to that of AMN arising before puberty, thus supporting a possible link between such types of nevi.

Number and size of acquired melanocytic nevi and affecting risk factors in cases admitted to the dermatology clinic

Introduction

The size and number of acquired melanocytic nevi (AMN) and presence of dysplastic nevi are the leading risk factors that should be recognized in the development of malignant melanoma.

Aim

To evaluate AMN and risk factors in the development of AMN in all age groups admitted to a dermatology outpatient clinic.

Material and methods

Four hundred and twelve patients who were admitted to the dermatology outpatient clinic for any dermatological symptom and who accepted to participate in the study were randomly included in the study. For each case, background-family history and dermatological findings were recorded. All AMN observed in the patients were dermatoscopically examined.

Results

The presence of more than 50 nevi was significantly higher in males, in individuals who had a history of sunburn and smokers. The number of nevi that were 5 mm and below was found to be higher in individuals who regularly sunbathed their face/body, in individuals using sunscreen, in individuals who had a history of sunburn, smokers and alcohol users. The number of nevi that were above 5 mm was higher in smokers. The total dermatoscopy score between 4.75 and 5.45 was found to be higher in individuals who had more than 50 nevi, in individuals exposed to more than one chemical substance and in alcohol users.

Conclusions

When determining the patient’s risk factors, factors such as the patient’s sunbathing habits and chemical substance exposure features should be taken into consideration besides the number and size of nevi.

Genetics of melanocytic nevi

Melanocytic nevi are a benign clonal proliferation of cells expressing the melanocytic phenotype, with heterogeneous clinical and molecular characteristics. In this review, we discuss the genetics of nevi by salient nevi subtypes: congenital melanocytic nevi, acquired melanocytic nevi, blue nevi, and Spitz nevi. While the molecular etiology of nevi has been less thoroughly studied than melanoma, it is clear that nevi and melanoma share common driver mutations. Acquired melanocytic nevi harbor oncogenic mutations in BRAF, which is the predominant oncogene associated with melanoma. Congenital melanocytic nevi and blue nevi frequently harbor NRAS mutations and GNAQ mutations, respectively, while Spitz and atypical Spitz tumors often exhibit HRAS and kinase rearrangements. These initial 'driver' mutations are thought to trigger the establishment of benign nevi. After this initial phase of the cell proliferation, a senescence program is executed, causing termination of nevi growth. Only upon the emergence of additional tumorigenic alterations, which may provide an escape from oncogene-induced senescence, can malignant progression occur. Here, we review the current literature on the pathobiology and genetics of nevi in the hope that additional studies of nevi promise to inform our understanding of the transition from benign neoplasm to malignancy.

Dermoscopy of black skin: A cross-sectional study of clinical and dermoscopic features of melanocytic lesions in individuals with type V/VI skin compared to those with type I/II skin

BACKGROUND

The identification of "normal" dermoscopic patterns of acquired melanocytic nevi provides better diagnostic accuracy for melanoma in people with black skin.

OBJECTIVE

We sought to describe melanocytic lesions (numbers and anatomic distributions) in skin types V and VI compared with skin types I and II, according to the Fitzpatrick classification. We sought to identify differences in dermoscopic findings in acquired melanocytic nevi (global pattern, pigment and color distribution) between the groups.

METHODS

We conducted cross-sectional, prospective, and consecutive data collection in 2 dermatologic outpatient clinics, between October 8, 2010, and March 20, 2013. From the 501 volunteers, 480 participants fulfilled the eligibility criteria. A total of 460 acquired melanocytic nevi were selected for dermoscopic analysis.

RESULTS

Individuals with skin type V/VI had fewer melanocytic lesions than those with skin type I/II (15.08 vs 7.90; P = .032), and the anatomic distribution in the first group was predominantly on the face and acral sites (P < .001). The acquired melanocytic nevi in the skin type V/VI group were associated with the reticular pattern (P < .0001), with a tendency toward central hyperpigmentation (P = .0025).

LIMITATIONS

The choice of a single representative nevus per patient is a limitation.

CONCLUSIONS

Acquired melanocytic nevi in individuals with skin type V/VI have a distinct dermoscopic pattern from those with skin type I/II.