Male breast cancer in Iceland.

All malignant tumours of the male breast diagnosed in Iceland during the 40-year period 1955-1994 were studied with regard to histological classification, tumour grading and flow cytometric analysis. Of 31 malignant tumours diagnosed, 29 were primary breast carcinomas. Male breast carcinoma constitutes 1% of all breast malignancies in Iceland and 0.25% of all malignant tumours in males. About 80% of the male breast carcinomas were diagnosed during the latter half of the study period. The mean age of the patients was 66.3 years and the left-to-right ratio was 1.9:1.0. Right-sided tumours appeared to be more aggressive. The mean tumour size was 2.6 cm. The vast majority of the carcinomas (79%) were of the infiltrating ductal type. Of these 21.7% were grade I, 43.5% were grade II and 34.8% grade III. Papillary carcinomas made up 17% of the total. These occurred in slightly older patients than the infiltrating ductal carcinomas and were diploid tumours. In this study 57% of the tumours were found to be aneuploid, but nearly 70% of the invasive ductal carcinomas NOS were aneuploid. In general, the aneuploid tumours were larger, of higher average histological grade and had a higher mean S-phase value. The overall mean S-phase fraction was 7.2% which is similar to that found in female breast tumours in Iceland. It is concluded that male-to-female ratio of breast carcinoma in Iceland is similar to that found in other Western countries. The age-standardised incidence has increased considerably in the last 20 years, in contrast to the rates reported from most other countries. Papillary tumours are unusually common in Icelandic males.