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Ghong, Kim, Lee, and Park: Supplementary Role of Ultrasonography and Intraoperative Frozen Section Analysis in Diagnosis of Follicular Variant of Papillary Thyroid Carcinomas
Original Article

Korean J Endocrine Surg 2016;16(3):57-63.

Published online: 10 December 2016

DOI: https://doi.org/10.16956/kjes.2016.16.3.57

Supplementary Role of Ultrasonography and Intraoperative Frozen Section Analysis in Diagnosis of Follicular Variant of Papillary Thyroid Carcinomas

Byeong-Ho Ghong1, Dong-Ju Kim1, Ok-Jun Lee2, 3, Jin-Woo Park1, 4

1Department of Surgery, Chungbuk National University Hospital, Cheongju, Korea

2Department of Pathology, Chungbuk National University Hospital, Cheongju, Korea

3Department of Pathology, Chungbuk National University, College of Medicine, Cheongju, Korea

4Department of Surgery, Chungbuk National University, College of Medicine, Cheongju, Korea

Correspondence: Jin-Woo Park Department of Surgery, Chungbuk National Univsersity Hospital, 776, 1 sunhwan-ro, Seowon-gu, Cheongju 28644, Korea Tel: ＋82-43-269-6033 Fax: ＋82-43-266-6037 e-mail: webjwpark@chungbuk.ac.kr

This work was supported by the intramural research grant of Chungbuk National University in 2015.

Received 1 June 2016       Revised 20 July 2016       Accepted 2 August 2016

Copyright © 2016 Korean Journal of Endocrine Surgery

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

The follicular variant of papillary thyroid carcinoma (FVPTC) is the most common variant of papillary thyroid carcinoma (PTC). Preoperative diagnosis of FVPTC is often confused with cPTC, follicular neoplasm (FN), and benign follicular lesion because of the paucity of nuclear changes of PTC and overlapping features with benign and other neoplastic follicular lesions. The aim of this study is to elucidate whether ultrasonography and/or intraoperative frozen section analysis (FSA) have a supplementary role in the diagnosis of FVPTC.

Methods

Fifty-five patients diagnosed with histologically confirmed FVPTC from January 2007 to December 2013 were identified. All patients had undergone either lobectomy with/without completion thyroidectomy or total thyroidectomy. Medical records, final histological reports and sonographic (US) findings were reviewed. All sonographic images, 53 fine needle aspiration cytology (FNAC) slides, and FSA slides for 24 cases were available for reexamination.

Results

Three histologic types of FVPTC were identified: encapsulated (n=39); infiltrative (n=15); and diffuse (n=1). There were two distinct sonographic patterns: FN-type (n=28) and PTC-type (n=27). The encapsulated type is more common in the FN-like pattern, compared to the PTC-like one (85.7% vs. 55.6%, P=0.009). Among the 24 cases in which sonographic images and FNAC and FSA slides were available for review, six cases (25%) were diagnosed as either FN in FNAC and suspicious PTC(R/O PTC)/PTC in FSA or R/O PTC/PTC in FNAC and FN in FSA. Among those 24 cases described above, 13 cases (54.2%) were diagnosed as either FN-type in US and R/O PTC/PTC in FNAC/FSA or PTC-type in US and FN in FNAC/FSA.

Conclusion

It is difficult to make a correct diagnosis of FVPTC before definitive treatment even with US, FNAC and FSA. However the possibility of FVPTC must be considered, especially when diagnoses in US, FNAC and FSA are different and include R/O PTC/PTC and FN in the same case.

Keywords: Papillary thyroid carcinoma, Follicular variant, Follicular neoplasm, Fine needle aspiration cytology, Ultrasonography, Frozen section analysis

References

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Fig. 1.
Histologic types of follicular variant of papillary thyroid carcinomas. (A) Encapsulated, (B) minimally infiltrative, (C) widely infiltrative, and (D) diffuse type. Cap = capsule; T = tumor (H&E, ×100).
kjes-16-57f1.tif
Fig. 2.
Sonographic patterns of follicular variant of papillary thyroid carcinomas. (A) A papillary thyroid carcinoma-like ultrasound (US) image shows an irregular hypoechoic nodule with microcalcifications in the left thyroid gland. (B) A follicular neoplasm-like US image shows a well-defined oval isoechoic nodule in the right thyroid gland.
kjes-16-57f2.tif
Table 1.
Histologic types and sonographic patterns in follicular variant of papillary thyroid carcinomas
Histologic types| Sonographic pattern
USFN-type USPTC-type Total
Encapsulated 24 (43.6%)* 15 (27.3%) 39 (70.9%)
 Full 7 5 12
 Partial 17 10 27
Infiltrative 4 (7.3%) 11 (20.0%) 15 (27.3%)
 Minimal 2 6 8
 Wide 2 5 7
Diffuse   1 (1.8%) 1 (1.8%)
Total 28 (50.9%) 27 (49.1%) 55 (100%)

USFN-type = follicular neoplasm-like sonographic pattern; USPTC-type = papillary thyroid carcinoma-like sonographic pattern.

* Encapsulated type is more common in USFN-type, compared to USPTC-Type (85.7% vs. 55.6%, P=0.009).

Table 2.
Comparison between results of fine needle aspiration cytology and frozen section analysis in follicular variant of papillary thyroid carcinomas
FNAC Frozen
Benign FN ＞R/O PTC Total
Benign/AUS, FLUS FN 2 (8.3%) 3 (12.5%) 2 (8.3%) 1 (4.2%) 2 (8.3%) 2 (8.3%) 6 (25.0%) 6 (25.0%)
＞R/O PTC 3 (12.5%) 4 (16.7%) 5 (20.8%) 12 (50.0%)
Total 8 (33.3%) 7 (29.2%) 9 (37.5%) 24 (100%)

FNAC = fine needle aspiration cytology; AUS = atypia of undetermined significance; FLUS = follicular lesion of undetermined significance; FN = follicular neoplasm; ＞R/O PTC = definitive or suspicious papillary thyroid carcinoma.

Table 3.
Cytologic diagnosis by FNAC according to proportion of cells with nuclear features of classic papillary thyroid carcinoma (NF) in follicular variant of papillary thyroid carcinomas
    NF＜50%
 NF≥50%
FNAC Non-PTC 8 57.1% 14 36.9%
  ＞R/O PTC 7 42.9% 24 63.1%
Total   15 100.0% 38 100.0%

P=0.357.

Non-PTC = cytologic diagnoses but papillary thyroid carcinoma; ＞R/O PTC = definitive or suspicious papillary thyroid carcinoma.

Table 4.
Comparison between results of fine needle aspiration cytology and frozen section analysis according to sonographic patterns in follicular variant of papillary thyroid carcinomas
    USFN-type (n=12)
 USPTC-type (n=12)
Frozen section analysis
Benign FN ＞R/O PTC Benign FN ＞R/O PTC
FNAC Benign/AUS/FLUS 2 (16.7%) 1 (8.3%)     1 (8.3%) 2 (16.7%)
  FN 1 (8.3%) 1 (8.3%)   2 (16.7%)   2 (16.7%)
  ＞R/O PTC 3 (25.0%) 3 (25.0%) 1 (8.3%)   1 (8.3%) 4 (33.3%)

FNAC = fine needle aspiration cytology; AUS = atypia of undetermined significance; FLUS = follicular lesion of undetermined significance; FN = follicular neoplasm; ＞R/O PTC = definitive or suspicious papillary thyroid carcinoma; USFN-type = follicular neoplasm-like sonographic pattern; USPTC-type = papillary thyroid carcinoma-like sonographic pattern.

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