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

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.