Cellular DNA content in normal human thyroid: a flow cytometric study based on frozen biopsy material.

A method is presented for preparing conventionally frozen biopsy material of thyroid tissue for flow cytometric measurement of DNA content in individual cells. The accuracy of the method was established by measuring cell suspensions of 24 biopsies of normal thyroid tissue from 20 patients. Biopsy material immersed in Histocon preservative solution prior to freezing was found to give better results than material frozen dry. All samples were found to have approximately the same modal DNA value (i.e. diploid), as determined by calibration of the fluorescence measurement with a standard of fluorescent microspheres. It was found that for an unknown sample, a deviation in modal DNA content of more than 13-14 per cent from diploid can be classified as significant by this technique.