Trajectories of premalignancy during the journey from melanocyte to melanoma

A stepwise progression from melanocytic precursors to cutaneous melanoma is a well-established model, based on decades of careful observation and morphological analysis. The steps identified are benign melanocytic naevus, dysplastic naevus, 'radial growth phase' melanoma (including melanoma in situ) and 'vertical growth phase' melanoma (also termed tumourigenic melanoma). Recent genomic data have refined the understanding of the steps of melanoma development and their relationship to one another. These data support the existence of dysplastic naevi as distinct lesions; suggest the importance of clonal dynamics in the precursor steps of melanoma; and confirm the carcinogenic role of ultraviolet radiation throughout early melanoma development and progression. In this review, the steps of melanoma development and progression are summarised and discussed in the context of recent genomic studies. This new understanding of melanoma pathogenesis that has been facilitated through careful correlation of morphological and molecular features will allow the identification and development of robust biomarkers to assist in more accurate diagnosis and prognostication of melanocytic tumours.

Dysplastic naevi: to shave, or not to shave? A retrospective study of the use of the shave biopsy technique in the initial management of dysplastic naevi

The management of dysplastic naevi is a controversial subject. This study sought to assess the usefulness of the shave biopsy technique in the initial management of dysplastic naevi, and to demonstrate the advantages over the punch biopsy technique. We report a retrospective observational study of histopathology specimens examined in one histopathology practice over a 14-month period. Patients who had a clinical diagnosis of 'dysplastic naevus', which had initially been biopsied using either a shave or punch biopsy, and then followed up with a full-thickness elliptical excision, were included in the study. Histopathological concordance between the shave and punch biopsy specimens and their respective follow-up elliptical excisions was compared. We found that 21 of 22 (95.5%) shave biopsies were concordant with their respective excision specimens, and that 29 of 41 (70.7%) punch biopsies were concordant with their respective elliptical excision specimens. Of the shave biopsy specimens reviewed, 66% showed that the dysplastic naevi were completely excised with the initial biopsy, compared with 21.2% of the punch biopsy specimens. These findings confirm that shave biopsies provide accurate diagnostic information in the assessment of dysplastic naevi. Shave biopsies enable the entire lesion to be submitted for histopathological assessment, improving the chances of an accurate diagnosis.

Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi

A systematic meta-analysis of observational studies of melanoma and one of the most important risk factors, the number of naevi, was conducted in order to clarify aspects of the aetiology of this disease. Following a systematic literature search, relative risks (RRs) were extracted from 46 studies published before September 2002. Dose-response random effects models were used to obtain pooled estimates. Sub-group analysis and meta-regression were carried out to explore sources of between-study variation and bias. Sensitivity analyses investigated the reliability of the results and any publication bias. Number of common naevi was confirmed an important risk factor with a substantially increased risk associated with the presence of 101-120 naevi compared with <15 (pooled Relative Risk (RR) = 6.89; 95% Confidential Interval (CI): 4.63, 10.25) as was the number of atypical naevi (RR = 6.36 95%; CI: 3.80, 10.33; for 5 versus 0). The type of study and source of cases and controls were two study characteristics that significantly influenced the estimates. Case-control studies, in particular when the hospital was the source for cases or controls, appeared to present much lower and more precise estimates than cohort studies.

Ocular pigmented findings in patients with dysplastic naevus syndrome

There is a growing body of evidence supporting the theory that cutaneous dysplastic naevus syndrome patients are at increased risk of developing not only skin but also uveal melanoma. The relationship between dysplastic naevus syndrome and ocular naevi needs to be clarified. In this study we investigated the ocular pigmented findings in patients with dysplastic naevus syndrome and compared the results with a control group (subjects without atypical moles) in order to investigate the frequency of ocular naevi among dysplastic naevi-bearing patients. A total of 152 dysplastic naevus syndrome patients were enrolled in our investigation. The control group consisted of 142 sex-, age- and skin type-matched healthy volunteers without cutaneous dysplastic naevi or skin melanoma. Conjunctival and uveal pigmented findings and iris colour were recorded during a detailed ophthalmic examination. A greater number of conjunctival naevi (3.2% versus 0%), iris naevi (5.2% versus 1.4%), iris freckles (17% versus 5.6%) and choroidal naevi (5.2% versus 0.7%) were detected in the dysplastic naevus syndrome group compared with the controls. The difference reached statistical significance in the case of conjunctival naevi, choroidal naevi and iris freckles. Our results confirm the hypothesis that dysplastic naevus syndrome patients might have overstimulation of their melanocytic system not only in the skin but also in the uvea, leading to increased benign (as well as rarely malignant) melanocytic proliferation. Dysplastic naevus syndrome patients should be screened by ophthalmologists because of the increased frequency of different ocular pigmented alterations.

A perspective on the dysplastic nevus controversy

In 1992 an impartial scientific panel concluded that the term "dysplastic nevus" has created significant confusion and thus has outlived its usefulness. This chapter reviews the evolution of the controversy and offers a basis for understanding the panel's recommendations.

UV induction of cyclobutane thymine dimers in the DNA of cultured melanocytes from foreskin, common melanocytic nevi and dysplastic nevi

We compared the induction of cyclobutane thymine dimers after exposure to 302 nm UV in foreskin-derived melanocytes and melanocytes from nevocellular nevi, as well as in melanocytes cultured from dysplastic nevi, precursor lesions of melanoma, derived from four, three and four individuals, respectively. Cyclobutane thymine dimers were quantified in situ by means of an immunofluorescence assay with a specific monoclonal antibody. A method was developed to compare separately performed experiments in a standardized manner. For melanocytes from each source, we demonstrated a linear relationship between UV dose and immunofluorescence. In nevocellular and dysplastic nevi, two subpopulations could be detected, distinguished by their nuclear size. Large nucleated nevocellular nevus cells were most susceptible to the induction of thymine dimers (49% higher induction compared to induction in foreskin melanocytes), while in normal-sized nuclei of these nevus cells the same induction of thymine dimers was found as in nuclei from foreskin melanocytes. In contrast, large nucleated dysplastic nevus melanocytes did not differ from the foreskin melanocytes, while normal-sized nuclei of dysplastic nevus cells showed a lower induction (32% lower induction than in foreskin melanocytes).

Regional distribution of common and dysplastic naevi in relation to melanoma site and sun exposure. A case-control study

The frequency of melanoma (CMM), and of common and dysplastic naevi (CN and DN) in areas of skin chronically, intermittently and rarely exposed to UV light was investigated in 121 melanoma patients (30-50 years) and 310 controls. Both cases and controls had significantly more CN in intermittently exposed areas than in areas chronically or rarely exposed. The ratio of observed to expected number of CMM was also highest in intermittently exposed skin (1.3 compared to 0.8 in chronically exposed and 0.5 in rarely exposed areas). Thus, intermittent UV exposure seems to have the most potent 'naevogenic' as well as carcinogenic effect on melanocytes. Nineteen per cent of controls and 56% of cases had naevi fulfilling the clinical criteria for DN. The distribution pattern of DN was clearly different from that of CN and does not accord with the idea that UV light is a major aetiological factor for DN. The probability of CMM significantly increased with the degree of relative clustering of CN (p less than 0.05) and of DN (p less than 0.01). This co-variation of naevi and CMM over the body surface might be the result of the local insults to the melanocyte system caused by UV light and/or to the fact that naevi are precursor lesions of CMM.

A relation between childhood sun exposure and dysplastic nevus syndrome among patients with nonfamilial melanoma

We studied 117 patients with nonfamilial melanoma to determine whether melanoma patients with dysplastic nevus syndrome might be distinguished, on the basis of solar exposure, from melanoma patients without dysplastic nevus syndrome. Study participants were interviewed and received a skin examination, which included a total count of nevi, a standardized assessment of clinically atypical nevi, and the excision of each patient's clinically most atypical nevus. Based on the histologic review of the clinically most atypical nevus, each patient was classified as to whether dysplastic nevus syndrome was present or absent. Childhood sunburn with blistering and childhood recreational sun exposure were found to be associated with dysplastic nevus syndrome. The results suggest that childhood sun exposure increases risk of melanoma by initiating the melanoma precursor syndrome.

Possible ultraviolet A-induced lentigines: a side effect of chronic tanning salon usage

A patient who developed lentigines after prolonged ultraviolet A (UVA) exposure in a tanning booth is described. The patient had no exposure to psoralens or furocoumarins. Histologic examination of a representative lentigo revealed melanocytic hyperplasia and cytologic atypia. Increased nevocytic activity with histologic dysplasia was present in several junctional nevi excised during the period of UVA exposure. Several studies have revealed significant effects of UVA on melanocytes. Patients should be cautioned to avoid tanning bed use in view of these potentially deleterious effects.

Dysplastic nevi and germ cell tumors of the testis--a possible further tumor in the spectrum of associated malignancies in dysplastic nevus syndrome

Even though the exact spectrum of tumors is not yet defined in the dysplastic nevus syndrome (DNS), the increasing frequency of associated cancers is remarkable. The observation of 4 patients with sporadic form of DNS suffering from seminoma or embryonal carcinoma of the testicle suggests that germ cell tumors of the testis represent another form of associated cancer in DNS.