Incidental cancer in multinodular goitre post thyroidectomy

Background. The risk of malignancy in patients with multinodular goitre (MNG) is approximately 7.2%. The gold standard for diagnosis of thyroid cancer is fine-needle aspiration biopsy (FNAB). Unsuccessful, inconclusive or suspicious results mandate further investigations. The concern is that with a benign FNAB result there is no indication for surgery unless the patient has compression symptoms or cosmetic issues, but the risk of missed malignancy is nevertheless present. Objective. To determine the prevalence and histological features of incidental cancers in patients who had thyroidectomy for MNG. Method. Records of patients who underwent thyroidectomy between January 2005 and December 2010 at Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa, were retrospectively reviewed. Data retrieved included demographic characteristics of the patients, type of thyroidectomy, thyroid function test results, FNAB cytology and final histology results. Result. A total of 166 thyroidectomies were performed on 162 patients, the majority (139) of whom were females. The mean age was 46 years (range 15-79 years). A total of 120 pre-operative FNABs were available for analysis, 78 of which were suggestive of benign nodular goitre; 70 benign FNAB results were histologically confirmed to be MNG after thyroidectomy. Incidental malignancy was found in four of 70 cases of MNG (5.7%); all were papillary carcinomas, predominantly (75.0%) the follicular variant. Conclusion. The risk of missing cancer in patients with MNG was 5.7%. The commonest histological subtype of thyroid cancer found in MNG was papillary carcinoma.