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Table of Contents
Definition / general | Diagnosis | Prognostic factors | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Molecular / cytogenetics descriptionCite this page: Jug R, Jiang X. Invasive encapsulated follicular variant (invasive EFVPTC). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/thyroidinvasiveEFVPTC.html. Accessed May 21st, 2019.
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)
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