Ninety-four cases of encapsulated follicular variant of papillary thyroid carcinoma: A name change to Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features would help prevent overtreatment

Abstract

Encapsulated follicular variant of papillary thyroid carcinoma is a common thyroid gland cancer, with a highly indolent behavior. Recently, reclassification as a non-malignant neoplasm has been proposed. There is no comprehensive, community hospital based longitudinal evaluation of encapsulated follicular variant of papillary thyroid carcinoma. Ninety-four cases of encapsulated follicular variant of papillary thyroid carcinoma were identified in a review of all thyroid gland surgeries performed in 2002 within the Southern California Permanente Medical Group. All histology slides were reviewed and follow-up obtained. Seventy-five women and nineteen men, aged 20-80 years (mean 45.6 years), had a single (n = 61), multiple (same lobe; n = 20), or bilateral (n = 13) tumor(s), ranging in size from 0.7 to 9.5 cm in diameter (mean 3.3 cm). Histologically, all cases demonstrated a well-formed tumor capsule, with capsular and/or lymphovascular invasion in 17 and no invasion in 77 cases. Lymph node metastases were not identified. The tumors had a follicular architecture, without necrosis or 43 mitoses/10 high-power fields (HPFs). Classical papillary thyroid carcinoma nuclear features were seen in at least three HPFs per 3 mm of tumor diameter, including enlarged, elongated, crowded, and overlapping nuclei, irregular nuclear contours, nuclear grooves, and nuclear chromatin clearing. Lobectomy alone (n = 41), thyroidectomy alone (n = 34), or completion thyroidectomy (n = 19) was the initial treatment combined with post-op radioablative iodine in 25 patients. All patients were without evidence of disease after a median follow-up of 11.8 years. Encapsulated follicular variant of papillary thyroid carcinoma showed benign behavior, supporting conservative surgery alone and reclassification of these tumors to Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP).

Programmed Death - Ligand 1 Expression Distinguishes Invasive Encapsulated Follicular Variant of Papillary Thyroid Carcinoma from Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features

“…Importantly, no significant difference in cytoplasmic PD-L1 expression between benign and NIFTP subgroups suggests that NIFTPs are more close to benign nodules, supporting the new paradigm for classification of NIFTP as non-malignant neoplasms (Maletta et al, 2016, Nikiforov et al, 2016, Patel, 2016, Thompson, 2016). The EFVPTC with invasion subgroup in which the cases were mainly classified as stage I and II at resection showed increased PD-L1 cytoplasmic staining.…”

“…The follicular variant of papillary thyroid carcinoma (FVPTC) is a heterogeneous group of tumors, including the infiltrating and encapsulated variants (Shi et al, 2016). The diagnosis of encapsulated FVPTC (EFVPTC) without invasion as a malignant lesion remains controversial (Hodak et al, 2016, Nikiforov et al, 2016, Thompson, 2016). The microscopic diagnostic criteria for EFVPTC are follicular architecture, widespread nuclear features of papillary carcinoma, some additional features (papillae, fibrous bands, dense eosinophilic colloid), and the presence of capsule (Shi et al, 2016).…”

Preoperative Cytologic Diagnosis of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Prospective Analysis

“…The recently introduced terminology of NIFTP (1) represents a paradigm shift in the diagnosis of PTC, recognizing that tumors previously classified as encapsulated, partially encapsulated or well-circumscribed FVPTC without capsular penetration or lymphovascular invasion have little, if any, metastatic potential or risk of recurrence (4,5,(10)(11)(12)(13). Furthermore, NIFTP tend to harbor RAS and PAX8/PPARc mutations and lack the BRAF V600E mutation that is associated with high-risk histopathologic features (14-16).…”

Encapsulated follicular variant of papillary thyroid cancer: are these tumors really benign?

“…6–8 Recent research shows that encapsulated form of FVPTC without invasion has an excellent prognosis with virtually no recurrence. 9–11 This observation lead to the change of FVPTC classification – non-invasive, encapsulated FVPTCs with certain additional features were reclassified to be “noninvasive follicular thyroid neoplasm with papillary-like nuclear features, or NIFTP”. 9 To provide more details about different histological variants, we retrospectively analyzed data.…”