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.
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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). |
![]() | 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. |
Table 1.
Histologic types and sonographic patterns in follicular variant of papillary thyroid carcinomas
Table 2.
Comparison between results of fine needle aspiration cytology and frozen section analysis in follicular variant of papillary thyroid carcinomas
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% |
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
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.