Dr. Nikiforov's clinical expertise is in thyroid tumors' pathology and genetics and molecular diagnostics of thyroid and other diseases. He serves as the co-director of the Multidisciplinary Thyroid Center at UPMC and as a national and international consultant on thyroid pathology. He is a senior editor of the textbook "Diagnostic Pathology and Molecular Genetics of the Thyroid," now in its 3rd edition. Aiming to decrease a large number of diagnostic thyroid surgeries performed for nodules with unclear cancer risk, he collaborated with Dr. Marina Nikiforova to invent a molecular test for thyroid nodules, the earliest version of which was launched clinically at UPMC in 2007. Now known as a ThyroSeq Genomic Classifier v.3, it is widely used in the U.S. and other countries. In 2014, Dr. Nikiforov formed and led an international group of pathologists and clinicians to reexamine a common type of low-grade thyroid cancer known as "Encapsulated Follicular Variant of Papillary Carcinoma." Based on the generated data, the group proposed in 2016 to reclassify this tumor as "Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP)", removing the word "cancer" from the diagnosis. The new entity was accepted by the World Health Organization in 2017. The reclassification is expected to affect annually >50,000 patients worldwide; it has contributed to the decreasing incidence of thyroid cancer in many countries observed over the last several years. Dr. Nikiforov served on the American Thyroid Association Taskforces that published the Anaplastic Thyroid Cancer Guidelines in 2012 and 2021, and Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer in 2016