Nuclear DNA analysis and prognosis in carcinoma of the thyroid gland. A nationwide study in Iceland on carcinomas diagnosed 1955-1990.

The purpose of this study was to ascertain whether DNA ploidy status and S-phase fraction affected the prognosis of patients with carcinoma of the thyroid gland. We reviewed all malignant thyroid tumours diagnosed in Iceland from 1955 to 1990. In all, 494 thyroid carcinomas were diagnosed during that period. By analysing tumour material from paraffin blocks by flow cytometry we were able to evaluate the ploidy status in 424 tumours and the S-phase value in 417 tumours. We detected aneuploid cell populations in 9.7% of papillary carcinomas, 24.3% of follicular carcinomas, 42.9% of medullary carcinomas and 78.6% of anaplastic carcinomas. Some 57% of tumours, mainly papillary carcinomas, had an S-phase value of less then 3%, whereas most of the other histological types of carcinoma, including all the anaplastic tumours, had an S-phase value of > or = 3%. Univariate analysis indicated that both ploidy status and S-phase fraction were significant variables. When taking into account known prognostic variables of thyroid carcinoma in a multivariate analysis, however, neither ploidy status nor S-phase value proved significant. We conclude that DNA ploidy status and S-phase values are not independent prognostic factors in thyroid carcinoma.