Thyroid tumors with follicular architecture

Thyroid tumors with follicular architecture encompass a considerable array of distinct entities. These lesions share significant morphologic overlap, but portend different prognostic and therapeutic implications. Due to their similar growth patterns, distinction between these tumors can be difficult; remarkable interobserver variability exists, even between expert endocrine pathologists. Given the diagnostic challenges associated with these lesions, establishment of the correct diagnosis requires adequate gross examination protocol, careful attention to morphologic features and pathologic context, as well as—increasingly—adjunct molecular findings. In this review, we summarize the salient features of various follicular thyroid tumors, with special emphasis on the recently defined category of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), as well as the molecular pathology of these lesions.