An update on noninvasive follicular thyroid neoplasm with papillary-like nuclear features.

PURPOSE OF REVIEW: Noninvasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) has been established in the literature as a clinically indolent tumor. Despite this, it was traditionally treated like all other PTCs. In an attempt to reduce overtreatment of this entity, a panel of experts reclassified this entity as noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP). This reclassification has led to a flurry of literature elucidating the molecular, cytologic and clinical parameters of this 'new' entity and the implications for patient management. The purpose of this review is to examine the latest literature on this tumor and explore how its emergence has impacted our current understanding of the diagnosis, management and outcomes in this entity. RECENT FINDINGS: NIFTP is a low grade tumor with an indolent clinical course. Recent studies have begun to document the variable incidence of NIFTP, the ultrasound and cytologic findings, and the impact of the NIFTP terminology on established rates of malignancy in fine-needle aspiration and clinical outcome studies. SUMMARY: The recent literature on molecular, radiographic and cytologic characteristics of NIFTP are building our understanding of this neoplasm and support its indolent nature.

Top Ten Oncocytic Head and Neck Lesions to Contemplate.

BACKGROUND: Oncocytes are a component of many metaplastic and neoplastic lesions throughout the head and neck area, primarily originating in salivary/seromucinous glands and the thyroid gland. In addition, other lesions can contain cells that mimic oncocytes (pseudo-oncocytes); these can be of epithelial or non-epithelial origin. METHODS: Review article. RESULTS: Oncocytic metaplasia is common in seromucinous glands throughout the upper aerodigestive tract, most notable in the oral cavity, nasopharynx and larynx. The main oncocytic salivary gland neoplasms are Warthin tumor and oncocytoma. Infarction of Warthin tumor may lead to recognition difficulties. Oncocytic subtypes of mucoepidermoid carcinoma and intraductal carcinoma have morphologic and immunohistochemical features that allow distinction from major oncocytic entities. Oncocytic thyroid tumors include adenoma, carcinoma (follicular, papillary and medullary), along with poorly differentiated tumors. Oncocytic papillary sinonasal and middle ear tumors must be distinguished from low grade adenocarcinomas. Pseudo-oncocytic entities include paraganglioma, Langerhans cell histiocytosis, giant cell tumor, rhabdomyoma, and metastatic tumors. CONCLUSIONS: Correct diagnosis of oncocytic head and neck lesions requires a knowledge of the spectrum of possible entities, their characteristic sites of occurrence, architecture, histomorphology, and immunohistochemistry. Oncocytic subtypes of several newly described entities are now recognized. Both epithelial and non-epithelial mimics of oncocytes exist. The molecular features of oncocytic tumors can be helpful in their diagnosis and understanding their pathogenesis.