Melanoma in Western Australia in 1980-81: incidence and characteristics of histological types.
All cutaneous malignant melanomas diagnosed in Western Australia in 1980-81 were reviewed and classified according to histological type (i.e., superficial spreading melanoma, Hutchinson's melanotic freckle melanoma (lentigo maligna melanoma), nodular melanoma and melanoma of unclassifiable type). The most common invasive melanoma was superficial spreading melanoma with an incidence rate of 14.3 per 100,000 person-years in females and 9.0 in males. It most commonly affected the trunk in males and the lower limbs in females and showed a peak incidence in middle life. Invasive Hutchinson's melanotic freckle melanoma was much less common than invasive superficial spreading melanoma (1.8 per 100,000 person-years in both sexes), occurred most commonly on the head and neck and increased progressively in incidence with age. Nodular melanomas were more frequent in men (4.5 per 100,000 person-years) than women (2.0). They were thicker than other types of invasive melanomas, showed more mitotic activity and had less evidence of regression. Their site distribution was similar to that of superficial spreading melanoma. In women the pattern of incidence with age was also similar to that of superficial spreading melanoma. In men it was more like that of Hutchinson's melanotic freckle melanoma. Melanomas of unclassifiable type did not have distinctive epidemiological features common to both sexes, although the trunk was the site most commonly affected in both men and women. With some exceptions the patterns of occurrence of in-situ lesions were similar to those of the corresponding invasive lesions. Benign melanocytic naevi were found less often in association with Hutchinson's melanotic freckle (melanoma) (6%) and nodular melanoma (9%) than with superficial spreading melanoma (22%) or melanoma of unclassifiable type (34%).