A publication of the American Thyroid Association

Summaries for Patients from Clinical Thyroidology by Ernest Mazzaferri, MD MACP
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Abbreviations & Definitions

Papillary microcarcinoma is a form of papillary thyroid cancer that is 1 cm (0.4 in) or smaller in diameter. However, this small tumor accounts for almost half of the thyroid cancers diagnosed in the past three decades. There are often multiple papillary microcarcinomas in the thyroid gland and up to 50% develop lymph-node metastases in the central and lateral areas of the neck. However, the 10-year mortality rates in patients with this tumor are in less than 1 %. Some patients develop invasive disease in the neck.

What is the study about? This is a study of papillary thyroid microcarcinoma, a tumor measuring 1 cm (0.4 in) or less in diameter, which has caused considerable debate regarding its diagnosis, treatment and long-term outcome.

The full article title: “Papillary microcarcinoma” It is in the May 2008 issue of World Journal of Surgery (Volume 32, Issue 5, pages 747-53. The authors are S Noguchi, H Yamashita., S Uchino, S Watanabe. The abstract can be obtained from:

What is known about the problem being studied? Although papillary thyroid microcarcinomas comprise almost half of the thyroid cancers diagnosed in the United States and Europe, there is debate regarding their management. Although long-term survival rates are in the range of 99%, a small but important number of patients develop metastasize and some have tumors invade the esophagus and nerves in the neck. Some have suggested this tumor requires no therapy.

What was the aim of the study? This large retrospective study was done to better understand the management of papillary microcarcinoma.

Who was studied? In all, 2070 patients with papillary microcarcinoma were studied among 4840 patients (43%) with papillary thyroid cancer, all of whom were treated with total or near-total thyroidectomy. Their median age at the time of surgery was 47 years (range, 11 to 83), and the male-to-female ratio was 1:8.9.

How was the study done? Patients were all treated and underwent follow-up at the Noguchi Thyroid Clinic and Hospital Foundation in Japan, where the authors perform over 1500 thyroid operations annually. The authors have been gathering follow-up data on thyroid cancer patients since 1922.

What were the results of the study? Although only 12% of the patients had lymph node metastases removed from the central part of the neck, about half of them were malignant. In all, only 3.5% of the patients experienced a recurrence after a median of 10.3 years, but the 30-year recurrence rate was 40% in patients older than 55 years and less than 10% in patients younger than 55 years. Recurrence rates after 35 years of follow-up were 3% and 14% for tumors 1 to 5 mm and 6 to 10 mm, respectively. Almost all of the recurrences were in the neck. Of 2070 patients who underwent follow-up for 16.5 ± 7.3 years, only 12 (0.6%) died of thyroid cancer. When the primary tumor adheres to or invades the recurrent laryngeal nerve, which controls the vocal cords, or the muscular layer of the esophagus, recurrence-free survival rate decreased significantly.

How does this compare with other studies? There no other studies of this magnitude and such large long-term follow-up.

What are the Limitations of this study? Radioiodine therapy was not given to the patients in this study, and thus no information is available on this point.

What are the implications of this study? Patients with papillary microcarcinoma older than 55 years have high tumor recurrence rates but low cancer-specific mortality rates. This tumor is similar to larger papillary thyroid cancers in which age-based recurrence rates extend for many years justifying long-term follow-up with neck ultrasonography.

The American Thyroid Association guidelines suggest total thyroidectomy for papillary microcarcinoma that is diagnosed preoperatively and for tumors that are metastatic or invasive

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