Efforts were made to further explain female superiority in survival of 753 patients with clinical Stage I malignant melanoma. Two factors contributing to this female superiority in survival drew some of their prognostic value from the correlation with tumor thickness. (1) More than twice as many women as men had primary lesions located on the extremities, which were prognostically favorable anatomical sites in both men and women. In addition, women with extremity lesions had a more favorable prognosis than men with extremity lesions. This sex differential in survival for patients with extremity lesions was partly attributable to the fact that the extremity lesions of women were significantly thinner than those of men.
(2) Significantly more women than men were under age 50; this age group of women had a significantly better prognosis than the corresponding age group of men. The sex differential in survival for patients under 50 years was partly attributable to the fact that the women's lesions were significantly thinner than those of men. There was only a slight sex differential in the survival of patients 50 years and over, a finding in consonance with the smaller difference in tumor thickness between these older men and women. The association between decline in prognosis with increasing age and decline in proportion of thin lesions with increasing age was much closer in men than women. In men and women matched by age, site, and thickness of primary lesions, women with very thick tumors still survived longer.