We evaluated the frequency of thyroid cancer in patients with cold thyroid nodules
in relation to iodine intake, sex, age, and multinodularity in a consecutive series
of patients with nodular thyroid diseases.
In the period from 1980 to 1990, 5,637 patients were studied: 4,176 patients were
from an iodine-sufficient area (ISA) and 1,461 from an adjacent iodine-deficient area
(IDA). Surgery was performed in 792 patients on the basis of a suspicious or malignant
finding at fine-needle aspiration biopsy.
The overall thyroid cancer frequency was 4.6% (259 patients had cancer). Iodine intake
affected the cancer rate in patients with cold nodules. The frequency of cancer in
patients with cold thyroid nodules was 5.3% in the ISA and 2.7% in the IDA. This difference,
however, was significant only in females. Sex had a major influence on the malignant
rate of cold nodules; although female patients were more frequently observed (n =
5,028) than male patients (n = 609), the frequency of cancer was significantly lower
in female patients with cold nodules (4.2%) than in males (8.2%). Age was an important
factor in both sexes. The proportion of nodules that were malignant was smallest in
patients of the 4th decade and was greatest in patients younger than 30 years or older
than 60 years. Multivariate analysis showed that sex and age interact in determining
the cancer risk in patients with thyroid nodules. Finally, the frequency of thyroid
cancer in patients with a solitary nodule was not different from the frequency in
patients with multiple nodules.
Our study indicates that thyroid cancer risk in a patient with a nodular goiter varies
markedly according to iodine intake, sex, and age but not in relation to multinodularity,
as assessed by clinical examination. The knowledge of these epidemiologic aspects
of thyroid cancer may increase the accuracy of the preoperative selection of patients
with cold nodules of the thyroid.