Preoperative diagnostic categories of fine needle aspiration cytology for histologically proven thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma: Analysis of cause of under- or misdiagnoses

Abstract

Cytologic diagnosis of thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma (FACHAC) is challenging due to cytomorphologic features that overlap with other follicular-patterned lesions. This study was designed to analyze diagnostic categories (DCs) of preoperative fine needle aspiration cytology (FNAC) of histologically proven thyroid FACHACs to evaluate under- or misdiagnoses in FNAC and elucidate potential causes for such phenomena. A total of 104 thyroid nodules with preoperative FNAC which were diagnosed as FACHAC in resection specimens were included in this study. Of these, 66 cases had also undergone thyroid core needle biopsy (CNB); FNAC and CNB DCs were compared in these cases. Various cytologic and histologic parameters were compared between the nodules with different FNAC DCs. After a review of FNAC slides, DCs were re-assigned in 20 (19.2%) out of the 104 cases. Of the 66 cases with CNB diagnoses which were mostly classified as lower DCs in FNAC, 31 (47.0%) were diagnosed as suspicious for a follicular neoplasm in CNB. Cases which were underdiagnosed in FNACs were associated with lower cellularity, predominant macrofollicular pattern, absence of microfollicles arranged in trabecular pattern, and absence of transgressing vessels in cytology smears. High cellularity, microfollicles arranged in trabecular pattern, nucleolar prominence, and large cell dysplasia were more frequently found in malignancy than in benign neoplasm. In conclusion, thyroid FACHACs seem to be under- and misdiagnosed in preoperative FNAC. Innate characteristics of the nodules were associated with under-diagnosis as well as the quality of the FNAC specimens. Certain cytomorphologic features can be helpful in differentiating malignancy among FACHACs.

Pre-Operative Cytological Evaluation of Thyroid Nodules According to the 2017 Bethesda System

“…FNA cytology is the most accurate and cost-effective method for evaluating thyroid nodules [1,2,5], It is useful for identifying features of papillary thyroid carcinoma, medullary and anaplastic thyroid carcinoma as well as other rare thyroid tumors [1,5]. Before the adoption of the TBSRTC in 2007, thyroid cytopathology reporting was following various classification schemes proposed by different scientific societies such as the Papanicolaou Society of Cytopathology and American Thyroid Association, the British Thyroid Association- Suspicious for follicular neoplasm 2…”

“…Despite the limitations of FNA cytology, secondary cytology features on thyroid FNA can raise the suspicion for FTC. These features include a hyper-cellular, monomorphic specimen with little to no colloid [5].…”

“…The incidence of thyroid cancer has increased worldwide in the past few decades [1][2][3]. FNA was recognized as a first-line diagnostic method for the evaluation of thyroid lesions in northern Europe during the period between 1950 and 1960 [2,4,5]. During the last 2 decades, its diagnostic value has been widely accepted.…”

“…During the last 2 decades, its diagnostic value has been widely accepted. Nowadays, FNA consists a very useful examination due to its high accuracy in the preoperative assessment of solitary thyroid nodules, contributing to the appropriate management of the patient by decreasing the number of unnecessary thyroidectomies [1,2,5]. It is estimated that thyroid carcinomas consist only 1, 5% of the total thyroid neoplasms and cause the 0, 4% of cancer deaths [1,2].…”

“…Thyroid carcinomas are further subclassified in papillary, follicular, medullary, Hurthle cell, undifferentiated and metastatic. Lymphomas have also been dignosed by FNA [2,5].…”