The frequency of thyroid gland invasion in advanced laryngeal malignancy: an audit of total laryngectomy histological specimens

Makepeace, A H
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Background Thyroid gland involvement in advanced laryngeal malignancies is a rare entity, mostly resulting from direct contiguous spread from anterior and inferior tumours. Reported practice is to perform a hemithyroidectomy at the time of laryngectomy. However, this results in pointless excision of functional tissue and the added morbidity of hypothyroidism post operatively. Aim The aim of this study is twofold: firstly, to assess the frequency of thyroid gland involvement in laryngectomy specimens from Chris Hani Baragwanath Hospital, and secondly, to determine any association between the anatomical subsites of tumour and thyroid gland involvement. Methods This is a retrospective clinical audit of histological reports on laryngectomy specimens collected over a 10 year period from January 2005 and December 2014. The study was conducted at Chris Hani Baragwanath Hospital, affiliated to the University of the Witwatersrand, in South Africa. ENT operating registries and the laboratory database were used to access all records of total laryngectomies done over the 10 year period. Seventy-three laryngectomies were done, 9 were excluded as no thyroid tissue was included in the sample and 1 was excluded due to inadequate demographic detail. Thus a total of 63 histological reports were included in the study. Data extracted included age, race, sex, pathological stage of tumour, thyroid gland involvement and anatomical subsites involved by tumour (subglottis, anterior commissure and transglottic tumours). Data was analysed using standard statistical methods including a Fischer-exact test and an ANOVA association test. Statistica software was used. Results Four of the 63 cases had thyroid gland involvement (6.35%). The majority of the patients were black males in the age group 50 to 60 years of age. The tumours were all advanced laryngeal malignancies and only 2 of the 63 cases were found to have a diagnosis of adenosquamous carcinoma and chondrosarcoma. None of the anatomical subsites were found to be statistically significant in association with thyroid gland involvement, however, this result was thought to be skewed due to the small number of tumours involving the thyroid gland. Conclusion In accordance with South African and international studies on the same topic, thyroid gland involvement in laryngeal tumours is a rare occurrence. Due to the complications of performing a thyroidectomy and the hypothyroidism that accompanies it, a thyroidectomy should not always be performed. However, due to the recurrence rates and poor prognosis of patients with stomal recurrence (associated with thyroid gland involvement), thyroidectomy still needs to be considered. Based on known anatomical pathways of extralaryngeal spread of tumours via the anterior commissure, paraglottic spaces and those tumours involving the subglottis, selected patients require thyroidectomy at the time of laryngectomy to achieve adequate oncological margins.
This dissertation is submitted as a final copy as the University’s Academic and Clinical supervisor