Prediction of malignancy in solitary thyroid nodules in a country with endemic goiter

High incidence of thyroid cancer in long-standing goiters with thyroglobulin mutations

In this paper, we report the high prevalence of thyroid malignancy in patients with thyroglobulin mutations in Japan. Mutations of the thyroglobulin gene cause defective thyroid hormone synthesis, resulting in congenital hypothyroidism. Since our report in 1999 on the thyroglobulin mutations C1264R and C1996S, we have identified 14 adult patients (7 males and 7 females) from 9 unrelated families. They visited hospitals for treatment of huge goiters that first appeared in childhood. Persistent growth of the thyroid gland, probably caused by thyrotropin (TSH) stimulation, partially compensated thyroid hormone production, resulting in lowered serum TSH concentrations in turn. Consequently, many patients had to undergo multiple operations. Of 11 patients who had undergone surgery, 7 had thyroid cancers. Of five patients whose thyroid tissue was available, we found a heterozygous activating mutation, either V599E or K600E, in cancerous tissue from each of 2 patients. From these observations, we conclude that goiter resulting from thyroglobulin mutations is associated with thyroid cancer.

Thyroid nodular lesion: analysis of cancer risk based on Kuma Hospital experience

It is a difficult question, whether it is malignant or not, when you follow up patients with thyroid nodular lesions. Cytological examination helps to solve this issue more accurately but a cancer risk still exists in patients with a negative cytology, non-diagnostic or suspicious follicular neoplasms. Analysis of cancer risk in patients with benign thyroid nodular lesions was carried out among 1044 cases who underwent thyroid surgery at Kuma Hospital, Kobe, Japan, in 2000. The purpose of this study was to provide evidence of cancer risk in those patients in Japan. Among the 356 cases with benign nodular lesions, 99 cases of papillary carcinoma were found in the thyroid parenchyma. Seventy-nine of the 99 cases were clinical cancer and were found preoperatively by cytology, while 20 out of 277 (7.22%) cases were found postoperatively as incidental carcinoma. The incidence of follicular carcinoma of a minimally invasive type in the index nodule was 22 out of 279 (7.89%) cases in patients who were surgically treated.

The role of iodine in carcinogenesis

Iodine is an essential nutrient for the normal growth and development of humans and animals and is necessary for normal metabolism and regulation of thyroid hormones. Iodine excess can produce thyrotoxicosis but not cancer. However, radioiodine is carcinogenic for the thyroid gland. Dietary iodine deficiency is associated with goiter in humans and animals. The goiter develops because of a feedback system between thyroid hormones, the pituitary gland, and the hypothalamus, and it regulates the synthesis and release of thyroid-stimulating hormone. Chronic hypersecretion of thyroid-stimulating hormone causes profound goiter (diffuse thyroid hyperplasia), which appears to be related to carcinogenesis. Chronic dietary iodine deficiency in rats leads to thyroid follicular adenomas by 12 months and follicular carcinomas by 18 months. An increased risk of thyroid cancer has been reported in humans with goiter and those living in some iodine-deficient areas of the world. In very recent animal studies, iodine deficiency, chemical goitrogens, and thyroid toxins have been shown to have potent tumor-promoting effects. In rats, iodine deficiency is a much more effective tumor promoter than it is a carcinogen, suggesting that a similar relationship may exist in human populations. These studies suggest that a major role of iodine is to prevent the formation of thyroid tumors in humans and animals.

Management of thyroid nodules. I: History and physical examination, blood tests, X-ray tests, and ultrasonography

The approach to the management of the thyroid nodule remains controversial. Confusion exists because virtually any thyroidal disease can present as a clinically solitary nodule which means there is no uniformity regarding natural history, incidence, prevalence, epidemiology, and pathophysiology.. The variety of definitions of thyroid nodules and thyroid carcinoma and the different modes of study selection and individual bias add to the confusion. Diagnostic approaches have not yielded a completely reliable technique to differentiate benign from malignant thyroidal disease. A history of neck irradiation of cervical lymphadenopathy significantly increases the chance of thyroid malignancy, but other parameters of the history or physical examination as well as blood tests are unreliable. Ultrasound displays anatomic but not histologic features. X-ray techniques (plain films, computed tomographic scans, xeroradiography, chest x-ray, barium swallow, lymphography, and angiography) have been used to visualize thyroid nodules, with some techniques proving more useful than others.