Dr Ghossein is the Director of Head and Neck Pathology at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York. His research focuses on improving the classification of thyroid carcinomas. He published the first article in 2006 demonstrating the extremely indolent outcome of the encapsulated non-invasive papillary carcinoma follicular variant leading to a reclassification of this entity as non-invasive follicular thyroid neoplasm with papillary like nuclear features (NIFTP). Dr Ghossein is the senior author of the NIFTP article published in JAMA Onc in 2016. He also developed a novel definition of poorly differentiated thyroid carcinoma. He published many articles on the stratification of encapsulated thyroid carcinoma into prognostically relevant groups. In collaboration with the Endocrinology and Surgery services at MSKCC, he helped characterize at the molecular level the follicular variant of papillary carcinoma, Hurthle cell, poorly differentiated and anaplastic thyroid carcinomas.