Dense fibrosis. Another diagnostic criterion for papillary thyroid carcinoma.

The follicular variant of papillary thyroid carcinoma poses a diagnostic problem when optically clear nuclei cannot be clearly identified. Grooved nuclei, though highly specific, are often difficult to identify among the typically overlapping nuclei of the papillary carcinoma. In the frozen sections, both characteristics are usually not seen. The present study attempted to analyze the association between dense, and frequently hyalinized, fibrosis and papillary carcinoma to assess the possibility of using this finding as another diagnostic criterion for this type of thyroid carcinoma. Histologic slides of 37 papillary and 28 follicular carcinomas of the thyroid were reviewed. The presence of dense fibrosis within the tumor masses was recorded, while peripheral fibrosis was ignored. The proportion of papillary carcinoma showing fibrosis within the tumor mass was compared with that of the follicular counterpart. The odds ratio was calculated, and chi 2 with Yates' correction was computed for statistical significance. Thirty-three (89.2%) of 37 cases of papillary carcinoma showed dense fibrosis within the tumor masses, giving an odds ratio of 37.95 compared with the follicular type. The association is very strong and highly significant. It is concluded that dense fibrosis within a malignant tumor of the thyroid can be used as another diagnostic criterion of papillary carcinoma, especially when other classic criteria are absent or inconspicuous.