[Carcinoma of the colon in Iceland 1955-1989. A study on pathology.]

The objective of this study was to investigate various pathological parameters of colon carcinoma in Iceland in the 35 year time period from 1955-1989, and changes in these parameters during the study period.

Information on all patients diagnosed with colon carcinoma in the study period was obtained from the Icelandic Cancer Registry. All pathology reports and autopsy reports were checked. All pathology samples were reviewed and the tumours reevaluated, reclassified, tumour location determined, the tumours graded and Dukes staged and age standardized incidence was calculated according to revised diagnosis. Cancers in polyps are included in the study. The study period was separated into seven five year periods and changes in pathological parameters investigated according to time periods.

After reevaluation of the tumours 1205 fulfilled the criteria for the diagnosis of colon carcinoma, 572 in men and 633 in women. The incidence increased in the study period for men from 8.2 to 21.5/105 and for women from 7.9 to 15.8/105. The pathological parameters were determined for 1109 tumours. Adenocarcinoma NOS was the most common diagnosis or 90.1% of the tumours and mucinous carcinomas came second. Most of the tumours were located in the sigmoid colon (38.6%), 19.1% in the coecum and 14.5% in the ascending colon. No significant observed changes occurred in tumour location in the study period. The mucinous histological type and signet ring tumour type were more common in the right colon. In Dukes staging of the tumours 9.1% were in stage A, 32.1% in stage B, 24.6% in stage C and 22.7% in stage D, whereas 11.5% proved indeterminate. A minimal trend to increase in Dukes A tumours was observed in the latter half of the study period, overall no significant changes in Dukes classification could be pinpointed in the time period. Most of the tumours were of intermediate tumour grade or 70.1%, but 16.5% were well differentiated and 13.4% were poorly differentiated. A much higher percentage of poorly differentiated tumours were present in the right colon in comparison to the left colon. A poorer differentiation of the tumours went hand in hand with worse Dukes stage of tumours.

We conclude that: 1. the incidence of colon carcinoma has much increased during the study period for both sexes, 2. observed changes in studied pathological parameters over the study period were minimal. Of interest is the minimal change in Dukes stages of colon cancer in the study period.