The impact of incomplete clinical information and initial biopsy technique on the histopathological diagnosis of cutaneous melanoma.

BACKGROUND/OBJECTIVES: Increased rates of histopathological misdiagnosis of melanoma have been associated with incisional punch more so than shave biopsy when compared with complete excisional biopsy. It is unknown how the increasing utilisation of shave biopsy may impact melanoma diagnosis. The extent to which the provision of clinical information to the pathologist may improve diagnostic accuracy remains unclear. This study assessed the impact of both initial biopsy technique and provision of adequate clinical information to pathologists on the accuracy of histopathological diagnosis of melanoma and disease progression. METHODS: We conducted a retrospective cohort with nested case-control study of all histopathological false-negative and false-positive melanoma diagnoses from January 2014 to May 2019 from the Victorian Melanoma Service electronic database. Cases were assessed for the initial biopsy type, provision of clinical information on pathology request forms and disease progression associated with false-negative diagnosis. RESULTS: Partial shave biopsy had higher odds of false-negative (OR 5.19, 95% CI 2.89-9.32; P < 0.001) and false-positive diagnoses (OR 1.95, 95% CI 1.45-2.63; P < 0.001) of melanoma when compared with elliptical excisional biopsy. These odds ratios were comparable with those found with incisional punch biopsy. Providing the suspected clinical diagnosis to pathologists also reduced the odds of false-negative diagnosis with melanoma progression by 3.8-fold (P = 0.02). CONCLUSION: The choice of initial biopsy technique and providing the suspected clinical diagnosis to pathologists are important for correct histopathological diagnosis of cutaneous melanoma and prevention of further disease progression.

Australian general practitioners' attitudes and knowledge of sentinel lymph node biopsy in melanoma management.

BACKGROUND AND OBJECTIVES: In Australia, the uptake of the sentinel lymph node biopsy (SLNB) appears low despite clinical practice guideline recommendations. The aim of this study was to describe the knowledge and attitudes of general practitioners (GPs) to SLNB. METHOD: GPs were recruited at an annual conference and a skin cancer skills workshop, and using GP professional communications. A mixed methods approach comprised a cross-sectional questionnaire and, for a subset of participants, semi-structured interviews. RESULTS: Overall, 231 GPs completed the questionnaire, of whom 23 were interviewed. One-third (32%) described themselves as quite or very familiar with the guidelines, and two-thirds (68%) thought that SLNB had an important role in the management of patients with melanoma. Of GPs who would discuss SLNB with eligible patients, <40% correctly identified that SLNB is recommended for patients with an invasive melanoma >1 mm thick. DISCUSSION: GPs were generally supportive of SLNB. Familiarity with the guidelines was low, particularly regarding which patients should be considered for SLNB.

Acral lentiginous melanoma: Clinicopathologic and survival differences according to tumour location.

BACKGROUND/OBJECTIVES: Acral lentiginous melanoma (ALM) is a melanoma subtype associated with atypical locations on the hands and feet and advanced disease at diagnosis. There is a limited understanding of whether the survival is similar for nail, non-nail, lower limb and upper limb ALM patients. We therefore explored clinicopathologic characteristics and melanoma-specific survival of ALM patients according to tumour location. METHODS: A prospectively collected cohort study was performed of all primary invasive cutaneous acral lentiginous melanomas with known thickness and tumour location reviewed at a tertiary referral centre over 21 years. RESULTS: A total of 101 ALM patients were reviewed from 1994 until 2016. The majority of cases (82/101) occurred on the feet. Hand ALMs were thicker and more likely to be ulcerated than feet ALMs (P = 0.05 and 0.02, respectively); however, survival was not statistically different between these two groups (univariate HR 0.48 P = 0.11, 95% CI, 0.20-1.17; multivariate HR 0.67 P = 0.40, 95% CI, 0.27-1.69, respectively). Non-nail ALM patients had longer survival when compared to nail ALM on univariate analysis (HR 0.40, 95% CI, 0.17 to 0.90) which was accounted for by Breslow thickness and ulceration (multivariate HR 0.56, 95% CI, 0.24 to 1.34). CONCLUSIONS: The reduced melanoma-specific survival in nail ALM patients was likely due to their greater thickness and ulceration. Although hand ALMs are thicker and more frequently ulcerated, this is likely due to the higher proportion of nail ALMs present in this location.

Identifying challenges to implementation of clinical practice guidelines for sentinel lymph node biopsy in patients with melanoma in Australia: protocol paper for a mixed methods study.

INTRODUCTION: Sentinel lymph node biopsy (SLNB) is a diagnostic procedure developed in the 1990s. It is currently used to stage patients with primary cutaneous melanoma, provide prognostic information and guide management. The Australian Clinical Practice Guidelines state that SLNB should be considered for patients with cutaneous melanoma >1 mm in thickness (or >0.8 mm with high-risk pathology features). Until recently, sentinel lymph node (SLN) status was used to identify patients who might benefit from a completion lymph node dissection, a procedure that is no longer routinely recommended. SLN status is now also being used to identify patients who might benefit from systemic adjuvant therapies such as anti-programmed cell death 1 (PD1) checkpoint inhibitor immunotherapy or BRAF-directed molecular targeted therapy, treatments that have significantly improved relapse-free survival for patients with resected stage III melanoma and improved overall survival of patients with unresectable stage III and stage IV melanoma. Australian and international data indicate that approximately half of eligible patients receive an SLNB. METHODS AND ANALYSIS: This mixed-methods study seeks to understand the structural, contextual and cultural factors affecting implementation of the SLNB guidelines. Data collection will include: (1) cross-sectional questionnaires and semistructured interviews with general practitioners and dermatologists; (2) semistructured interviews with other healthcare professionals involved in the diagnosis and early definitive care of melanoma patients and key stakeholders including researchers, representatives of professional colleges, training organisations and consumer melanoma groups; and (3) documentary analysis of documents from government, health services and non-government organisations. Descriptive analyses and multivariable regression models will be used to examine factors related to SLNB practices and attitudes. Qualitative data will be analysed using thematic analysis. ETHICS AND DISSEMINATION: Ethics approval has been granted by the University of Sydney. Results will be disseminated through publications and presentations to clinicians, patients, policymakers and researchers and will inform the development of strategies for implementing SLNB guidelines in Australia.

The anatomic distribution of cutaneous melanoma: A detailed study of 5141 lesions.

BACKGROUND/OBJECTIVES: There is evidence that cutaneous melanomas at different anatomic sites present with distinctive clinicopathologic features. We examined the anatomic distribution of cutaneous melanoma and its variation by patient characteristics, subtype and Breslow thickness, using high-resolution anatomic site data. METHODS: A cross-sectional study was performed of all primary cutaneous melanoma cases managed at a tertiary referral centre, analysing prospectively collected clinical data across 50 anatomic subsites. RESULTS: The study included 5141 in situ or invasive melanomas; most were invasive (76.2%), and the median Breslow thickness of invasive lesions was 1.0 mm. Superficial spreading (57.2%), lentigo maligna (20.8%) and nodular (12.2%) were the most common histopathological subtypes. Sun-exposed sites such as the female nose and cheek, the male ear, as well as the upper back in both sexes had the highest incidence of melanoma per unit area. When compared to the posterior forearm, the scalp, ear, preauricular, perioral, subungual and plantar sites had thicker invasive melanomas (each P < 0.05). The peri-auricular, ear and cheek had the highest incidence of nodular melanoma per unit area. There were subtype-, age- and sex-specific differences in melanoma anatomic distribution. CONCLUSION: Melanoma most commonly arises in sun-exposed facial areas, as well as the upper back. Increased thickness is found for melanoma in acral and many head and neck sites. Nodular melanoma is more likely to occur in head and neck sites including the peri-auricular area, ear and cheek. Clinicians should carefully assess these sites during skin examinations.

The increasing use of shave biopsy for diagnosing invasive melanoma in Australia.

OBJECTIVE: To assess changes in the choice of skin biopsy technique for assessing invasive melanoma in Victoria, and to examine the impact of partial biopsy technique on the accuracy of tumour microstaging. DESIGN: Retrospective cross-sectional review of Victorian Cancer Registry data on invasive melanoma histologically diagnosed in Victoria during 2005, 2010, and 2015. SETTING, PARTICIPANTS: 400 patients randomly selected from each of the three years, stratified by final tumour thickness: 200 patients with thin melanoma (< 1.0 mm), 100 each with intermediate (1.0-4.0 mm) and thick melanoma (> 4.0 mm). MAIN OUTCOME MEASURES: Partial and excisional biopsies, as proportions of all skin biopsies; rates of tumour base transection and T-upstaging, and mean tumour thickness underestimation following partial biopsy. RESULTS: 833 excisional and 337 partial diagnostic biopsies were undertaken. The proportion of partial biopsies increased from 20% of patients in 2005 to 36% in 2015 (P < 0.001); the proportion of shave biopsies increased from 9% in 2005 to 20% in 2015 (P < 0.001), with increasing rates among dermatologists and general practitioners. Ninety-four of 175 shave biopsies (54%) transected the tumour base; wide local excision subsequently identified residual melanoma in 65 of these cases (69%). Twenty-one tumours diagnosed by shave biopsy (12%) were T-upstaged. With base-transected shave biopsies, tumour thickness was underestimated by a mean 2.36 mm for thick, 0.48 mm for intermediate, and 0.07 mm for thin melanomas. CONCLUSION: Partial biopsy, particularly shave biopsy, was increasingly used for diagnosing invasive melanoma between 2005 and 2015. Shave biopsy has a high rate of base transection, reducing the accuracy of tumour staging, which is crucial for planning appropriate therapy, including definitive surgery and adjuvant therapy.

Improving diagnostic accuracy for suspicious melanocytic skin lesions: New Australian melanoma clinical practice guidelines stress the importance of clinician/pathologist communication.

BACKGROUND: Incorrect or delayed diagnosis of melanoma may lead to inappropriate treatment, poor clinical outcomes, increased cost and medicolegal consequences. The provision of pertinent clinical information is essential for accurate pathological diagnosis of cutaneous melanocytic tumours. Failure to provide this information may contribute to poor outcomes. OBJECTIVE: The aim of this article is to highlight important clinical information that clinicians can provide to pathologists to facilitate accurate diagnosis of melanocytic tumours. DISCUSSION: Pertinent clinical information includes patient age, sex, tumour site, specimen orientation (if appropriate), history of the lesion, presence of any clinically or dermoscopically suspicious areas within the lesion (including apparent regression), access to any relevant clinical and/or dermoscopic photographs and prior pathology reports, melanoma history and risk factors, and history of concurrent or recent pregnancy. If the clinical features are not concordant with the pathology findings, the clinician and pathologist should discuss the case to identify the reason for incongruence.

Anatomic location of primary melanoma: Survival differences and sun exposure.

BACKGROUND: Anatomic location of melanoma has been shown to independently influence melanoma-specific survival (MSS). OBJECTIVE: We aimed to compare the MSS of specific anatomic subsites and between chronically, intermittently, and rarely sun-exposed sites. METHODS: A prospective cohort study was performed of primary invasive cutaneous melanomas with known thickness and location reviewed at a tertiary referral center over 21 years. RESULTS: Overall, 3570 primary cutaneous invasive melanoma cases were included. After adjustment for clinicopathologic variables (including thickness, ulceration, mitotic rate, sex, age, and subtype), posterior scalp melanoma was associated with worse MSS (hazard ratio [HR], 2.46; 95% confidence interval [CI], 1.38-4.40) compared with the upper back, whereas melanoma on the thighs, forearms/hands, and anterior upper arms had better MSS. Intermittent (HR, 0.56; 95% CI, 0.41-0.76) and chronically sun-exposed sites (HR, 0.70; 95% CI, 0.51-0.96) had improved survival compared with rarely exposed sites on multivariate analysis. LIMITATIONS: Potential selection bias of a tertiary referral center selecting for advanced cases. CONCLUSION: Altered MSS in the posterior scalp, thighs, forearms, hands, and anterior upper arms appears to be independent of clinicopathologic factors. Results were similar for both sexes and age groups. The posterior scalp should be considered a poor prognosis site.

Accuracy of partial biopsies in the management of cutaneous melanoma.

BACKGROUND: The recommended method for histopathological diagnosis of cutaneous melanoma is excisional biopsy, although partial biopsies (shave and punch) are often used. Following a partial biopsy, treatment guidelines recommend a narrow excisional biopsy to plan definitive management. There is limited evidence on the benefits of direct wide local excision (WLE) following diagnostic partial biopsies. METHODS: Retrospective cohort study of cutaneous melanoma cases, from two tertiary referral centres from January 2013 to December 2015. Demographic and histopathological data, including tumour thickness (T-stage) from initial biopsy and subsequent excisions, were collected. Logistic regression was used to examine histopathological T-staging between biopsy and subsequent excisions (upstaging). RESULTS: 2304 melanomas (2157 patients) were identified; 455 shave, 308 punch, 14 incisional and 1527 excisional biopsies. Out of 1527, 5 (<1%) excisional biopsies were upstaged from original biopsy T-stage to final WLE; compared to 28/455 (6%) for shave, 45/308 (15%) for punch and 2/14 (14%) for incisional biopsies. Histopathology upstaging were increased with punch (OR, 52.1; 95% CI, 20.5-132.4. P < 0.001) and shave biopsy (OR, 20.0; 95% CI, 7.7-52.0. P < 0.001) compared to excisional biopsy. Upstaging rates of 9.4% for desmoplastic (OR, 6.9; 95% CI, 2.4-19.7. P < 0.001) and 21.9% for acral lentiginous (OR, 18.4; 95% CI, 6.9-49.2. P < 0.001) melanomas were elevated compared to 1.4% for superficial spreading melanoma. CONCLUSIONS: In most cases, partial biopsy (particularly shave biopsy) can provide sufficient information to plan for definitive surgical melanoma management. Punch and incisional biopsies have elevated upstaging rates, a consideration in planning therapy. Partial biopsies of desmoplastic or acral lentiginous melanomas have high rates of upstaging and should have a complete excision prior to definitive treatment.

Methods of melanoma detection and of skin monitoring for individuals at high risk of melanoma: new Australian clinical practice.

INTRODUCTION: The evidence-based national clinical practice guidelines for the management of cutaneous melanoma published in 2008 are currently being updated. This article summarises the findings from multiple chapters of the guidelines on different methods of melanoma detection and of monitoring the skin for patients at high risk of melanoma. Early detection of melanoma is critical, as thinner tumours are associated with enhanced survival; therefore, strategies to improve early detection are important to reduce melanoma-related mortality. MAIN RECOMMENDATIONS: Clinicians who perform skin examinations for the purpose of detecting skin cancer should be trained in and use dermoscopy. The use of short term sequential digital dermoscopy imaging to detect melanomas that lack dermoscopic features of melanoma is recommended to assess individual melanocytic lesions of concern. The use of long term sequential digital dermoscopy imaging to detect melanomas that lack dermoscopic features of melanoma is recommended to assess individual or multiple melanocytic lesions for routine surveillance of high risk patients. The use of total body photography should be considered in managing patients at increased risk for melanoma, particularly those with high naevus counts and dysplastic naevi. There is insufficient evidence to recommend the routine use of automated instruments for the clinical diagnosis of primary melanoma. MANAGEMENT OVERVIEW: Determining the relative indications for each diagnostic method and how each method should be introduced into the surveillance of a patient requires careful consideration and an individualised approach.

Dermoscopy improves diagnostic accuracy for clinically amelanotic nodules.

BACKGROUND/OBJECTIVES: Amelanotic nodular melanomas are notoriously difficult to diagnose and are responsible for a disproportionate burden of melanoma mortality. It is important to distinguish them from other amelanotic nodules. This study aimed to describe the dermoscopic features of a series of nodular melanomas and other amelanotic nodules and to determine whether dermoscopy improves diagnostic accuracy. METHOD: Retrospective analysis of 150 clinically amelanotic nodules with macroscopic and dermoscopic images. RESULTS: In terms of classifying the nodules as malignant, dermoscopy was superior to unaided eye (specificity 89%; 95% CI 71-98% vs 67%; 95% CI 46-83%, P = 0.03). Dermoscopy enhanced sensitivity for the diagnosis of both amelanotic melanoma and SCC. In 19% of cases, using dermoscopy, the most likely diagnosis was changed from incorrect to correct. This included 26% of amelanotic melanomas which had a macroscopic misdiagnosis overturned to the correct diagnosis. Polymorphous vascular structures were more common in malignant nodules. 76% of amelanotic melanomas/Merkel cell carcinomas had polymorphous vessels compared with 38% of SCCs/KAs/BCCs and 22% of benign nodules (P < 0.001). CONCLUSION: Dermoscopy improves diagnostic accuracy for amelanotic melanomas and other amelanotic nodules. Although dermoscopy improves diagnostic accuracy for amelanotic melanomas, these aggressive melanomas remain diagnostically difficult.

Clinically amelanotic or hypomelanotic melanoma: Anatomic distribution, risk factors, and survival.

BACKGROUND: The recognition and diagnosis of clinically amelanotic or hypomelanotic melanoma is a challenge. OBJECTIVE: This study aimed to examine the anatomic distribution and risk factors associated with clinically amelanotic or hypomelanotic melanoma and compare the survival of patients with clinically amelanotic or hypomelanotic melanoma with that of patients with pigmented melanoma. METHODS: A prospective cohort study of all cases of primary invasive melanoma managed at a tertiary referral center was performed. RESULTS: There were a total of 3913 invasive melanomas, and 384 (9.8%) were clinically amelanotic or hypomelanotic. Skin phototype I; red as well as blonde hair color; actinic keratoses; nodular, desmoplastic, and lentigo maligna subtype; increased Breslow thickness; and mitoses were independently associated with amelanotic or hypomelanotic melanoma (P < .05). After adjustment for subtype and thickness, the face, ears, lateral aspect of the neck, upper portion of the arm, posterior aspect of the forearm, dorsal aspect of the hand, and anterior aspect of the lower portion of the leg were associated with increased odds of amelanotic or hypomelanotic melanoma when compared with the upper portion of the back (P < .05). Mortality risk from melanoma appeared greater for amelanotic or hypomelanotic melanoma than for pigmented melanoma (hazard ratio, 1.5; 95% confidence interval, 1.1-2.1) but was similar once Breslow thickness was taken into account. LIMITATIONS: Single tertiary referral center. CONCLUSION: Although clinically amelanotic or hypomelanotic melanoma can occur on all body sites, it is more common on chronically sun-exposed areas. Clinicians should have an increased index of suspicion in patients with a sun-sensitive skin phenotype, red hair, and associated actinic keratoses.

Tumour mutation status and melanoma recurrence following a negative sentinel lymph node biopsy.

BACKGROUND: A proportion of patients develop recurrence following a tumour-negative sentinel lymph node biopsy (SLNB). This study aimed to explore whether melanoma patients with BRAF or NRAS mutant tumours have an increased risk of developing disease recurrence following a negative SLNB compared to patients with wild-type tumours. METHODS: Prospective cohort study of melanoma patients at three tertiary referral centres in Melbourne, who underwent SLNB. Clinical, pathological and molecular characteristics and recurrence data were prospectively recorded. Multivariate Cox proportional hazards regression models estimated the adjusted hazard ratio (aHR) and corresponding 95% confidence interval (CI) for the association between mutation status and development of recurrence following a negative-SLNB. RESULTS: Overall, 344/477 (72.1%) patients had a negative SLNB. Of these, 54 (15.7%) developed subsequent recurrence. The risk of disease recurrence following a negative SLNB was increased for patients with either a BRAF or NRAS mutant tumour compared to wild-type tumours (aHR 1.92, 95% CI: 1.02-3.60, p = 0.04). CONCLUSION: Melanoma patients with BRAF or NRAS mutant tumours had an increased risk compared to patients with BRAF/NRAS wild-type tumours of developing disease recurrence following a tumour-negative SLNB. The findings also confirm the importance of continued surveillance to monitor for disease recurrence among SLNB-negative patients.

Concordance of somatic mutational profile in multiple primary melanomas.

This study aimed to determine the frequency and concordance of BRAF and NRAS mutation in tumours arising in patients with multiple primary melanoma (MPM). Patients with MPM managed at one of three tertiary referral centres in Melbourne, Australia, from 2010 to 2015 were included. Incident and subsequent melanomas underwent mutation testing. Cohen's kappa (κ) coefficient assessed agreement between incident and subsequent primary melanomas for both BRAF and NRAS mutation status (mutant versus wild-type). Mutation testing of at least two primary tumours from 64 patients was conducted. There was poor agreement for both BRAF and NRAS mutation status between incident and subsequent melanomas (κ = 0.10, 95% CI -0.10 to 0.42; κ = 0.06, 95% CI -0.10 to 0.57, respectively). In view of the low concordance in BRAF mutation status between incident and subsequent melanomas, mutational analysis of metastatic tissue, rather than of a primary melanoma, in patients with MPM should be used to guide targeted therapy.

Primary Tumor Thickness is a Prognostic Factor in Stage IV Melanoma: A Retrospective Study of Primary Tumor Characteristics.

INTRODUCTION: Stage IV melanoma exhibits a diverse range of tumor biology from indolent to aggressive disease. Many important prognostic factors have already been identified. Despite this, the behavior of metastatic melanoma remains difficult to predict. We sought to determine if any primary tumor characteristics affect survival following the diagnosis of stage IV melanoma. METHODS: All patients diagnosed with stage IV melanoma between January 2003 and December 2012 were identified from the Victorian Melanoma Service database. Retrospective chart review was performed to collect data on primary tumor characteristics (thickness, ulceration, mitotic rate, melanoma subtype, or occult primary). Known and suspected prognostic factors were additionally collected (time to diagnosis of stage IV disease, age, sex, stage, receipt of chemotherapy, and era of recurrence). The effect of primary tumor characteristics on overall survival from the date of diagnosis of stage IV disease was assessed. RESULTS: A total of 227 patients with a median follow-up of 5 years from diagnosis of stage IV disease were identified. Median overall survival of the cohort was 250 days.Of the primary tumor characteristics assessed, only tumor thickness affected survival from diagnosis of stage IV disease, hazard ratio=1.09 (1.02 to 1.16), P=0.008. This remained significant in multivariate analysis, P=0.007. Other primary tumor characteristics did not significantly influence survival. CONCLUSIONS: Primary tumor thickness is a significant prognostic factor in stage IV melanoma. Our data suggest that the biology of the primary melanoma may persist to influence the behavior of metastatic disease.

Clinical practice guidelines for the diagnosis and management of melanoma: melanomas that lack classical clinical features.

INTRODUCTION: A Cancer Council Australia multidisciplinary working group is currently revising and updating the 2008 evidence-based clinical practice guidelines for the management of cutaneous melanoma. While there have been many recent improvements in treatment options for metastatic melanoma, early diagnosis remains critical to reducing mortality from the disease. Improved awareness of the atypical presentations of this common malignancy is required to achieve this. A chapter of the new guidelines was therefore developed to aid recognition of atypical melanomas. Main recommendations: Because thick, life-threatening melanomas may lack the more classical ABCD (asymmetry, border irregularity, colour variegation, diameter > 6 mm) features of melanoma, a thorough history of the lesion with regard to change in morphology and growth over time is essential. Any lesion that is changing in morphology or growing over a period of more than one month should be excised or referred for prompt expert opinion. Changes in management as a result of the guidelines: These guidelines provide greater emphasis on improved recognition of the atypical presentations of melanoma, in particular nodular, desmoplastic and acral lentiginous subtypes, with particular awareness of hypomelanotic and amelanotic lesions.

Nodular melanoma is less likely than superficial spreading melanoma to be histologically associated with a naevus.

OBJECTIVES: To determine the frequency of naevus-associated melanoma among superficial spreading and nodular subtypes; and to investigate associations between naevus-associated melanoma and other clinico-pathological characteristics. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study of all patients with nodular and superficial spreading melanomas diagnosed between 1994 and 2015 at the Victorian Melanoma Service, Melbourne. METHODS AND MAIN OUTCOME MEASURES: Clinical and pathological characteristics of naevus-associated and de novo melanomas were assessed in univariable and multivariable logistic regression analyses. RESULTS: Of 3678 primary melanomas, 1360 (37.0%) were histologically associated with a naevus and 2318 (63.0%) were de novo melanomas; 71 of 621 nodular (11.4%) and 1289 of 3057 superficial spreading melanomas (42.2%) were histologically associated with a naevus. In multivariable analyses, the odds of being associated with a naevus were higher for melanomas located on the trunk (v head and neck: adjusted odds ratio [OR], 2.27; 95% CI, 1.73-2.96; P < 0.001), while the odds were lower for thicker tumours (adjusted OR, 0.75 per millimetre increase in Breslow thickness; 95% CI, 0.69-0.81; P < 0.001), amelanotic/hypomelanotic melanomas (adjusted OR, 0.68; 95% CI, 0.48-0.97; P = 0.035), and older age (patients 70 years or older v patients under 30 at diagnosis: adjusted OR, 0.28; 95% CI, 0.20-0.40; P < 0.001). After adjusting for confounders, the odds of an associated naevus was three times as high for superficial spreading melanomas as for nodular melanomas (adjusted OR, 3.05; 95% CI, 2.24-4.17; P < 0.001). CONCLUSION: Melanomas are most likely to arise in the absence of a pre-existing naevus, particularly nodular melanomas. Public health campaigns should therefore emphasise the detection of suspicious de novo lesions, as well as of changing lesions.