The History of the Follicular Variant of Papillary Thyroid Carcinoma

CONTEXT: The purpose of this review is to provide the historical context to recent developments in the classification of the follicular variant of papillary thyroid carcinoma (FVPTC), an entity that has long created significant controversy. The scope is to illustrate the evolution of the diagnostic criteria for papillary thyroid carcinoma, clarifying the role of molecular analysis, and the impact on patient management. EVIDENCE ACQUISITION: A PubMed search using the terms "follicular variant" and "papillary thyroid carcinoma" covering the years 1960-2016 was performed. Additional references were identified through review of the citations of the retrieved articles. EVIDENCE SYNTHESIS: The encapsulated/well demarcated non-invasive form of FVPTC that occurs annually in 45,000 patients worldwide was thought for 30 years to be a carcinoma. Many studies have now shown almost no recurrence in these non-invasive tumors, even in patients treated by surgery alone without radioactive iodine therapy. The categorization of the tumor as outright cancer has led to aggressive forms of treatment, with their side effects, financial costs, and the psychological and social impact of a cancer diagnosis. Recently, the encapsulated/well demarcated non-invasive, FVPTC was renamed as "Non-invasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) by an international group of experts. The new terminology lacks the carcinoma label enabling clinicians to avoid aggressive therapy. By taking the reader through the history of FVPTC, this article explains how diagnostic criteria for thyroid carcinoma of follicular cells have evolved over the last 60 years. It discusses the steps that led to the labeling of FVPTC as cancer and highlights the various studies that helped reclassify and rename this tumor. CONCLUSIONS: The encapsulated/well demarcated non-invasive form of FVPTC was thought to be a carcinoma for 30 years. By understanding the history of FVPTC, future classification of tumors will be greatly improved.