Non-invasive follicular thyroid neoplasm with papillary-like nuclei: reducing overtreatment by reclassifying an indolent variant of papillary thyroid cancer

Worldwide the rising incidence of cancer is attributed to ageing populations, environmental and lifestyle factors, and increased cancer surveillance. Cancer surveillance leads to increased early detection of indolent cancers, and in some cases to cancer ‘overdiagnosis’.1 In the thyroid, the increased incidence of thyroid cancer and cancer detection is primarily due to widespread use of thyroid ultrasound.2 This excess of newly diagnosed thyroid cancers occurs almost entirely because of greater detection of papillary thyroid cancers, a tumour which under the microscope shows a characteristic papillary growth pattern together with typical nuclear features. Follicular variant of papillary thyroid carcinoma (FVPTC) is one of two major subtypes of papillary thyroid cancer. The encapsulated type of FVPTC (eFVPTC), a tumour that under the microscope shows no invasion of surrounding thyroid, blood vessels or lymphatics, has increased in incidence 2–3 times over the last 20–30 years. eFVPTC is now estimated …