19th January 2018, Volume 131 Number 1468

Miriam Karalus, Jade AU Tamatea, Helen M Conaglen, Michael Dray, Goswin Y Meyer-Rochow, John V Conaglen, Marianne S Elston

Multinodular goitre (MNG) is common particularly in iodine-deficient regions.1 Animal studies demonstrate an increased proliferative rate of thyroid follicular cells in iodine deficiency, suggesting that low iodine intake may promote…

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Summary

In this paper we assessed the rates of thyroid cancer identified by the pathologist after surgical removal of the thyroid gland when cancer was not suspected prior to surgery. Removal of the thyroid was performed for a reason other than the suspicion of cancer such as pressure symptoms from a large gland (goitre) or overactivity of the gland. Of the group with normal thyroid hormone levels, 8% had an incidental thyroid cancer and of those with an overactive thyroid gland, 10% of patients has a thyroid cancer identified on routine pathological assessment of the specimen. Most of these incidental cancers were small and of a type which would be expected to be unlikely to alter survival even if diagnosis had been delayed.

Abstract

Previously the risk of concomitant thyroid cancer in multinodular goitre (MNG) has been reported as approximately 4%. Cancer risk in toxic MNG was often considered lower than for non-toxic MNG, due to a possible protective effect of TSH suppression. However, recent American data suggest an approximately 18% risk of occult malignancy in both toxic and non-toxic MNG.

Aim

To assess malignancy risk in a New Zealand population undergoing thyroidectomy for MNG.

Method

Single-centre study of patients undergoing thyroidectomy for MNG from 1 December 2006 to 30 November 2016.

Results

Six hundred and two patients underwent surgery for MNG (448 non-toxic and 154 toxic). Of these, 95/602 (16%) had thyroid cancer. After excluding patients operated for preoperative suspicion for cancer, 30/401 (8%) patients with non-toxic MNG and 15/151 (10%) with toxic MNG had unsuspected or occult thyroid cancer (p=0.358). Patients with toxic MNG were less likely to undergo preoperative fine needle aspiration than those with non-toxic MNG (34% vs 52%, respectively p=0.0001). Two-thirds of unsuspected thyroid cancers were incidental micropapillary carcinomas and unlikely to alter survival irrespective of therapy.

Conclusion

Malignancy rates in MNG are higher than historically reported, although most unsuspected cancers are unlikely to alter mortality even if diagnosis is delayed.

Author Information

Miriam Karalus, Medical Student, Waikato Clinical Campus, University of Auckland, Hamilton;
Jade AU Tamatea, Endocrinologist, Waikato Clinical Campus, University of Auckland, Hamilton;
Helen M Conaglen, Senior Research Fellow, Waikato Clinical Campus, University of Auckland, Hamilton; Goswin Y Meyer-Rochow, Endocrine Surgeon, Waikato Clinical Campus, University of Auckland, Hamilton; John V Conaglen, Endocrinologist, Waikato Clinical Campus, University of Auckland, Hamilton; Marianne S Elston, Endocrinologist, Waikato Clinical Campus, University of Auckland, Hamilton.

Acknowledgements

MK was supported by a Waikato District Health Board Summer studentship award, administered by the Waikato Clinical Campus, Faculty of Medical & Health Science, University of Auckland. No other funding.

Correspondence

Dr Marianne Elston, Waikato Clinical Campus, Waikato Hospital, Private Bag 3200, Hamilton 3240.

Correspondence Email

marianne.elston@waikatodhb.health.nz

Competing Interests

Nil.

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