INCIDENCE OF CUTANEOUS MELANOMA IN THE CENTER OF ITALY - ANATOMIC SITE DISTRIBUTION, HISTOLOGIC TYPES AND THICKNESS OF TUMOR INVASION IN A REGISTRY-BASED STUDY

The majority of epidemiological data on cutaneous melanoma (CM) derives from studies carried out in a predominantly fair-skinned population. On the contrary, little is known of the epidemiological figures (including incidence data) in mediterranean populations. The aim of this study was to investigate the incidence rates of CM in a geographically-defined area of the centre of Italy, with particular attention to anatomic site distribution, histologic types and thickness of tumour invasion. After revision of the data base of the Tuscany Cancer Registry concerning the period 1985 to 1987, 282 incident cases of invasive CM (135 males, 147 females) were found in a resident population of 1,174,121 inhabitants. The mean annual age-standardized rates were 6.7/100,000 for males and 7.0/100,000 for females. Site-specific incidence rates showed an almost three-fold higher incidence of CM of the trunk in males than females (3.7/100,000 vs 1.4/100,000). Conversely, a four-fold higher incidence in females than in males was observed for the lesions of lower limb (2.1/100,000 vs 0.5/100,000). A statistically significant difference of incidence rates was also observed for the thigh (females 1.1/100,000, males 0.2/100,000), a normally sun-exposed area. Concerning histologic types of CM, the incidence of the nodular type was higher in males than in females (1.8/100,000 vs 1.3/100,000), even if the difference was not statistically significant in any class of age. The most interesting finding of this study was related to the difference of the thickness of tumour invasion between sexes at the time of diagnosis: lesions with favourable prognosis (less than 0.75 mm in thickness) were more frequent in females than in males (1.4/100,000 vs 0.3/100,000); on the other hand, incidence rates of poor prognosis CM (> 3.0 mm) were higher in males than in females (2.1/100,000 vs 1.0/100,000). This study shows that in mediterranean populations the specific incidence rates for age and anatomic site are similar to a predominantly fair-skinned population, whereas the overall incidence is lower. In respect of the peculiarity of each sex, the striking difference between males and females of the thickness of tumour invasion at diagnosis should be considered to better tailor further information for secondary prevention.