Thyroid Research Thyroid Research Archive Thyroid Cancer

Multifocal papillary carcinomas usually arise from one clone of thyroid cells

(July 2006)

The background of the study. Patients with papillary carcinoma of the thyroid may have small foci of carcinoma in their thyroid gland addition to their main tumor, which may represent spread of the main tumor or independent tumors. In this study, the relationships between tumors in the same patient were studied using analysis of three genes and X-chromosome inactivation.

How the study was done. Papillary-carcinoma tissue from 23 women was analyzed. The largest tumor in each woman ranged from 0.3 to 4.5 cm in diameter, and they had from one to five smaller noncontiguous tumors (total, 64) confined to the thyroid gland. Tumor and normal thyroid tissue were identified on microscope slides, DNA was extracted from the tissue, and a polymorphic gene on each of three different chromosomes was amplified. The pattern of X-chromosome inactivation was determined by amplification of its constituent androgen-receptor gene and detection of active and inactive forms of this gene.

The results of the study. The genetic composition of all the tumors was similar, indicating common parentage, in 20 of the 23 women (87 percent). They included 1 woman with 5 tumors, 1 with 4 tumors, and 7 with 3 tumors. In the 1 woman with 6 tumors, the results were similar in 5.

The pattern of X-chromosome inactivation was similar in all the tumors in 19 of the 20 women (95 percent). In 6 women, all the tumors had both an active and an inactive X chromosome; in 13, all the tumors had only an active or only an inactive X chromosome.

The conclusions of the study. In many patients with multifocal papillary thyroid carcinoma, the genetic composition of each tumor is the same, suggesting common parentage and therefore that tumors can spread within the thyroid.

The original article. McCarthy RP, Wang M, Jones TD, Strate RW, Cheng L. Molecular evidence for the same clonal origin of multifocal papillary thyroid carcinomas. Clin Cancer Res 2006;12:2414-8.