Nodular type and older age as the most significant associations of thick melanoma in Victoria, Australia.

OBJECTIVES To explore the clinical associations of thick melanoma and to compare the clinicopathological variables of nodular and superficial spreading types. DESIGN Cross-sectional study of all invasive primary melanomas recorded by the Victorian Cancer Registry for 1998 and those reviewed by the Victorian Melanoma Service between October 1, 1994, and April 31, 1999. SETTING Population-based cancer registry and public hospital-based multidisciplinary melanoma clinic. PATIENTS This study included 1422 patients recorded by the Victorian Cancer Registry and 674 patients who had attended the Victorian Melanoma Service; unclassifiable tumor types were excluded, leaving 1144 and 645 patients, respectively, eligible for analysis. MAIN OUTCOME MEASURES Melanomas were categorized by thickness into thin (< or =1 mm), intermediate (>1-3 mm), and thick (>3 mm) and compared according to patient age, sex, and tumor type and site. Superficial spreading and nodular types were also compared in this manner. Use of the Victorian Melanoma Service database enabled a more comprehensive analysis of historical and phenotypic characteristics. RESULTS Thick melanoma was predominantly nodular, occurring in older men, mostly on the head and neck and associated with fewer nevi. Nodular melanoma was thicker and found mostly on the lower limbs or head and neck; it had a greater association with a history of solar keratoses than did superficial spreading melanoma. CONCLUSION Nodular type and older age are the most significant associations of thick melanoma.