Differential diagnosis between follicular adenoma and follicular carcinoma of the thyroid by marker features.

Morphometric features descriptive of nuclear morphology, nuclear chromatin texture and nuclear staining density were studied in tissues from encapsulated follicular carcinoma and follicular adenoma of the thyroid, whose differentiation is one of the most difficult tasks in thyroid pathology. Measurements were made on nuclei in both tumorous and normal-appearing areas in the same section from six patients with each diagnosis, as well as on nuclei in sections from six normal individuals. The average nuclear optical density (OD) was significantly lower in the follicular carcinomas than in the follicular adenomas while the nuclear area was significantly increased in the carcinomas. The variance of the nuclear OD values was higher in both tumor and normal-appearing areas in the sections from the follicular adenomas than in the follicular carcinomas; this variance was lowest in tumor areas from the follicular carcinomas. There were also significant differences in another chromatin feature (the average difference in OD values between adjacent pixels) between nuclei from follicular carcinomas and those from follicular adenomas, whether comparing measurements between the tumor areas or between the histologically normal-appearing areas of the sections. These results suggest that the high-resolution study of marker features, such as nuclear chromatin and staining density, may help in the differentiation between follicular adenoma and encapsulated follicular carcinoma of the thyroid.