COMPARISON BETWEEN LENTIGO MALIGNA MELANOMA AND OTHER HISTOGENETIC TYPES OF MALIGNANT-MELANOMA OF THE HEAD AND NECK

A study of 953 invasive cutaneous malignant melanomas of the head and neck was performed to determine differences between lentigo maligna me lanoma and other histogenetic types with regard to patients and sites affected; prognosis was analysed in 595 of these cases. The cases stud ied comprised all head and neck melanomas registered with the Scottish Melanoma Group between 1979 and 1992, apart from the 3% of cases that were unclassifiable or rare histogenetic types. The histogenetic type s of melanoma were 498 (52%) lentigo maligna melanoma (LMM), 237 (25%) superficial spreading melanoma (SSM) and 218 (23%) nodular melanoma ( NM). Al types increased in incidence throughout the study period. Pati ents with LMM (mean age 73 years) and NM (mean 68 years) were signific antly older than those with SSM (mean 57 years). There were significan t anatomical subsite differences related to sex of patients and histog enetic type of melanoma; melanomas on the face were more frequent in f emales and 90% of LMM occurred at this site, whereas melanomas on the scalp, neck and ears were more frequent in men. Kaplan-Meier estimates of the probability of survival were produced for the 595 of these 953 patients with 5 year follow-up details. In this group of patients the prognostic significance of tumour thickness, Clark level of invasion, ulceration, histogenetic type of melanoma and number of mitoses were studied using stepwise variable selection of procedures. Each of these possible prognostic factors attained individual significance but the tumour thickness was the dominant risk factor in the proportional haza rds analysis. When patients were divided into four sex/ulceration subg roups (male/ulcerated, female/ulcerated, male/non-ulcerated, female/no n-ulcerated) and analysed by proportional hazards analysis, no variabl e other than the tumour thickness had any further prognostic effect. H istogenetic type did not remain an independent prognostic variable al this stage. Despite sex and subsite differences, the prognosis for inv asive lentigo maligna melanoma does not differ from that for other his togenetic types after controlling for tumour thickness.