Mod Pathol. 2016 Jul;29(7):698-707.
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 3mm 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).
PubMed ID: 27102347
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