Immunohistochemical markers in thyroid cancer in the Maltese population

Abstract

Thyroid tumours account for 90% of endocrine malignancies, however they have a favourable prognosis, accounting for a survival rate of more than 90%. Therefore, a proper and early diagnosis is crucial to improve the patients’ quality of life and prognosis and also avoid significant burden on the public health system. An overview of the epidemiology, demographics and investigations routinely used in the diagnosis of thyroid cancers was carried out. The latest guidelines regarding investigations and management were summarised and later compared and contrasted with the management of the studied cases. FNAB is currently the gold-standard investigation for thyroid nodules. The cytology provided from this investigation aids in classifying the nodule using the Bethesda System. The diagnosis of thyroid tumours is made on histological features, however the distinction between benign and malignant is not always straightforward. Due to this, immunohistochemical markers were introduced to aid in the diagnosis of thyroid carcinoma. Three of these important markers described in the literature are HBME-1, Galectin-3 and RET/PTC. HBME-1, (Hector Battifora mesothelial-1) is an unelucidated membrane antigen found in the microvilli of mesothelial cells. It has gained popularity in the past decade and has been studied to investigate its expression in benign and malignant thyroid lesions. In normal thyroid tissue there is no expression of HBME-1, however, it is overexpressed in malignant thyroid tumours especially papillary thyroid carcinoma. Galectin-3 is a protein which binds to cell surface glycoproteins and has recently received significant attention for its utility as a diagnostic marker in thyroid neoplasms. RET/PTC is a family of oncogenes arising from rearrangements in the gene on chromosome 10q, which are specific to papillary carcinomas and present in up to 77% of these tumours. The positive predictive value indicates a true positive case where there is papillary thyroid carcinoma and the markers are also positive. The negative predictive value indicates a true negative, where a case is benign and the markers do not stain. These values together with their sensitivity and specificity were calculated for all markers. The commonest type of thyroid carcinoma was found to be papillary thyroid carcinoma both in 2008 and 2013. In 2013, the number of ultrasounds and FNAB increased with a subsequent increase in diagnosis of papillary thyroid microcarcinoma. Both Galectin-3 and HBME-1 were found to stain significantly in papillary thyroid carcinoma, making them useful markers in diagnosing this type of thyroid carcinoma.