Is thyroid malignancy more frequent in solitary nodules?

Topic: NODULES & CANCER

Title: Prevalence and distribution of carcinoma in patients with solitary and multiple thyroid nodules on sonography.

Authors: Frates MC, Benson CB, Doubilet PM, Kunreuther E, Contreras M, Cibas ES, Orcutt J, Moore FD Jr, Larsen PR, Marqusee E, Alexander EK.

Reference: Journal of Clinical Endocrinology and Metabolism 91: 3411-3417, 2006

Summary

Background

Thyroid nodules are common, being detected by palpation in 3 to 7% of the adult population. Diagnostic evaluation and management of patients with multiple thyroid nodules is continually changing with new paradigms for improved care.

Purpose

The objectives of this study were to determine the prevalence, distribution, and frequency of malignancy in solitary and multiple thyroid nodules.

Results

A total of 1,985 patients with 3,483 nodules were evaluated. All patients had one or more thyroid nodules >10 mm. The prevalence of cancer was similar between patients with a single nodule (175/1,181 patients: 14.8 %) and patients with multiple nodules (120/804: 14.9). A solitary nodule was more likely to be malignant than a non-solitary nodule (P< 0.01). A nodule that was one of several had a lower likelihood (P< 0.001) of being malignant than did a solitary nodule: 175/1,181 solitary nodules (14.8 %) were malignant, as compared to 187/2,302 multiple nodules (8.1 %).

Conclusions

In a patient with one or more thyroid nodules larger than 10 mm in diameter, the likelihood of malignancy per patient is independent of the number of nodules in the gland, whereas the probability of malignancy decreases as the number of nodules increases.

Commentary

The prevalence of thyroid cancer in thyroid nodules is between 5-15 %. Recent studies using ultrasonographic-guided FNA cytology report a 7-14 % prevalence of thyroid cancer and suggest that neither nodule size nor number of nodules influences the likelihood of malignancy. For example, one study reported that cancer was present in 9.2 % of solitary lesions and in 6.3 % of multinodular goiters, a difference that was not significant. Recent guidelines by the A.A.C.E. emphasize that nodule selection for biopsy should be based on ultrasound (US) features rather than either nodule size or number.

The present study evaluated one or more thyroid nodules (>10 mm) evaluated by US-FNA cytology, and reported that the risk of malignancy was similar in a given patient whether single or multiple nodules are present. The study suggested that in a patient with one or more thyroid nodules (>10 mm), the likelihood of cancer per patient was independent of the number of nodules, whereas the probability of cancer per nodule decreased as the number of nodules increased. Moreover, clinical parameters were also important determinants of malignancy. For example, a nodule in a man was significantly more likely to be malignant than a similar lesion in a woman; patient age, however, did not correlate with the likelihood of malignancy. Sonographic features associated with malignancy include nodule composition, calcifications, and vascularity examined by color Doppler. The more cystic a nodule was, the less likely it was to be malignant, and completely cystic nodules were never malignant in this study population. The authors recommended that in patients with multiple thyroid nodules, -all nodules should be biopsied when up to three nodules larger than 10 mm in maximal diameter are present.- The authors call into question whether non-calcified, predominantly or completely cystic nodules need to undergo FNA cytology.

This study illustrates several points in the evaluation and management of nodular thyroid disease. US is critical in selecting nodules for biopsy, and lesions with highest sonographic risks should be the one(s) chosen to undergo FNA. When multiple nodules are present, more than one nodule may need to be sampled. In patients with multiple nodules malignancy is not always present in the predominant nodule. ( Summary and commentary prepared by Hossein Gharib ) Present summary and commentary are related to the Chapter N- 18 of TDM Full paper obtainable at www.jcem.endojournals.org/cgi/content/full/88/8/3531