Invasive encapsulated follicular variant (invasive EFVPTC)

Thyroid gland
Papillary carcinoma
Invasive encapsulated follicular variant (invasive EFVPTC)

Authors: Rachel Jug, M.D. and Xiaoyin "Sara" Jiang, M.D., FCAP (see Authors page)

Revised: 23 February 2017, last major update May 2016

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: invasive encapsulated follicular variant of papillary thyroid carcinoma

Table of Contents

Cite this page: Invasive encapsulated follicular variant (invasive EFVPTC). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/thyroidinvasiveEFVPTC.html. Accessed May 21st, 2018.

Definition / general

Prognostically distinct entity from counterpart NIFTP (non invasive follicular thyroid neoplasm with papillary-like nuclear features)

Diagnosis

Same nuclear features and follicular architecture as NIFTP but with vascular or tumor capsule invasion present

Prognostic factors

Good prognosis
Based on an international, multidisciplinary, retrospective study in which 101 participants had invasive EFVPT, 12 patients experienced an adverse event (including 5 patients developing distant metastases and 2 patients dying of the disease) by a median follow up time of 13 years (JAMA Oncol 2016;2:1023)

Gross description

Well circumscribed encapsulated solid nodules (Head Neck Pathol 2011;5:51)
Capsular invasion may or may not be grossly evident (Head Neck Pathol 2009;3:86)

Microscopic (histologic) description

Tumor invades capsule or extends into adjacent thyroid tissue, OR has evidence of lymphovascular invasion
Nuclear features of papillary thyroid carcinoma:
- Size and shape: nuclear enlargement / overlapping / crowding, elongation
- Nuclear membrane irregularities: irregular contours, grooves, pseudoinclusions
- Chromatin characteristics: clearing with margination / glassy nuclei
Follicular growth pattern may be microfollicular, normofollicular or macrofollicular with abundant colloid

Microscopic (histologic) images

Images hosted on PathOut servers:

With capsular invasion

Contributed by Andrey Bychkov, M.D., Ph.D.:

Vesicular nuclei with irregular membranes

Evident major and minor diagnostic features

Dark colloid with frequent scalloping and clefting

Free floating of small tumor fragment in vascular lumen

Small piece of tumor floats in vascular lumen

Capsular invastion and extrathyroidal extension

Tumor plug is associated with thrombus

High power (40×) H&E images demonstrating nuclear features of PTC:

Overlapping, elongation and a single mitotic figure

Irregular nuclear contours, grooves, pseudoinclusions

Clear chromatin with margination

Cytology description

FNA samples are usually hypercellular with neoplastic cells containing nuclear features of papillary thyroid carcinoma arranged in microfollicles
Nuclear features are more subtle than conventional papillary thyroid carcinoma
Colloid may be present
Cannot distinguish invasive EFVPTC from NIFTP on cytology, as cannot evaluate capsule on FNA

Molecular / cytogenetics description

Shares molecular features (RAS type mutations) with follicular adenoma, follicular carcinoma (Mod Pathol 2010;23:1191)