Clinical correlates of Breslow thickness of malignant melanoma

Background Breslow thickness is a major predictor of prognosis in cutaneous malignant: melanoma (MM) and patients continue to present with thick lesio ns, which have a poorer prognosis, Objectives To investigate correlations of Breslow thickness with demographi c variables, tumour site, clinical features, false negative diagnostic rate and clinic of primary referral. Methods Data were obtained from the records of 738 patients with histologic ally diagnosed cutaneous MM. Tumours included were in. situ and invasive MM and lentigo maligna melanoma. In view of the skewed distribution of MM thi ckness, categories of MM thickness were used for analysis, using the common ly applied cut-offs of 0.75, 1.5 and 3.5 mm. The variables investigated wer e particularly associated with changes in the proportion of the thickest gr oup, 'thick' MMs. The proportion of this thickness category is proposed as an appropriate and sensitive variable for the investigation of correlations with MM thickness. Thickness greater than or equal to1.5 mm has also been considered in view of its prognostic significance. Results Results were similar for the two thickness groups, but more significant for the thick group. The previously described correlations of tumour thickness and increasing age (P < 0.00001) and location on head and neck (P = 0.0002 ), together with the independence of these variables, have been confirmed. The correlation with male gender was also confirmed but this was weak (P = 0.05). Novel findings were correlations of Breslow thickness with all featu res of the seven-point checklist (P varying from P = 0.01 to P < 0.00001) a nd tumour elevation (P < 0.00001). In general in the seven-point checklist, the absence of the major features (except variation in size) (P < 0.00001) and presence of minor features (except altered sensation) (P varying from P = 0.004 to P < 0.00001) were strongly associated with thick MMs. These re sults for tumour thickness are a further argument for retention of the mino r features of the seven-point checklist. False negative diagnosis was found to be correlated with tumour thickness (P < 0.02) but this relationship wa s lost on multivariate analysis with inclusion of the clinical features. MM thickness was highly correlated with primary referral clinic (P < 0.00001) . Only <approximate to> 8% of MMs presenting to the Pigmented Lesion Clinic (PLC) were thick, while the proportion presenting to general dermatology w as about three times greater and to plastic surgery about five times greate r. This was maintained on multivariate analysis, including all other variab les and, therefore, there must be other determining factors of referral not examined in the study. Conclusion MM thickness is associated with increasing age, male gender, loc ation on the head and neck, all features of the seven-point checklist, tumo ur elevation and referral to the PLC. It is important to investigate furthe r the reasons for general practitioner referral of different thickness MM t o different types of clinic, as referral to clinics other than the PLC resu lts in delay in the first hospital appointment, and it is now apparent that thicker lesions are disproportionately affected.