Thyroid Research Thyroid Research Archive Thyroid Cancer

The characteristics and course of pure papillary carcinoma and follicular variant of papillary carcinoma are similar

(July 2003)

The background of the study. There are two major subtypes of papillary carcinoma of the thyroid, so-called pure papillary carcinoma and follicular variant of papillary carcinoma. The latter has been recognized with increasing frequency in recent years, but whether its biology is similar to that of pure papillary carcinoma is not clear. In this retrospective study, the characteristics and outcome of patients with the two subtypes were compared.

How the study was done. The study subjects were 243 patients with papillary carcinoma treated at a single oncology center in Israel between 1972 and 1990. Sections of all tumors were reviewed by several pathologists. The tumor was classified as a pure papillary carcinoma if it was composed of papillae lined by cells with nuclei that were enlarged and overlapped one another, and the nuclei had a thick nuclear membrane, small nucleoli next to the nuclear membrane, intranuclear grooves, and intranuclear inclusions. The tumor was classified as a follicular variant of papillary carcinoma if it was composed primarily of follicles (80 percent or more) and the nuclei of the cells had at least two of the features of papillary carcinoma. All patients had undergone total or near-total thyroidectomy, and 226 patients in whom postoperative imaging revealed uptake of radioactive iodine (I-131) received a therapeutic dose of I-131; later treatment varied according to the presence and site of recurrence.

The results of the study. There were 143 patients (59 percent) with pure papillary carcinoma and 100 patients (41 percent) with follicular variant of papillary carcinoma. There were no differences in the characteristics of the patients, the size of the tumors, or the frequency of multifocal tumors in the two groups. The median follow-up was 138 months (range, 48 to 288). The overall 21-year survival rates were, respectively, 82 percent in the patients with pure papillary carcinoma and 86 percent in the patients with the follicular variant of papillary carcinoma. Among several prognostic factors, only age was a determinant of poor outcome in either group, but there was no difference between groups.

The conclusions of the study. Patients with pure papillary carcinoma and follicular variant of papillary carcinoma do not differ in age, sex, or extent of tumor at the time of diagnosis, nor is their prognosis different.

The original article. Zidan J, Karen D, Stein M, Rosenblatt E, Basher W, Kuten A. Pure versus follicular variant of papillary thyroid carcinoma: clinical features, prognostic factors, treatment, and survival. Cancer 2003;97:1181-5.