Improving the diagnostic accuracy of thyroid follicular neoplasms: Cytological features in fine‐needle aspiration cytology

Abstract

Cytological diagnosis in follicular neoplasms of the thyroid has to surmount some difficulties. Capsular/vascular invasions or metastasis are the histological criteria for follicular carcinoma (FC), and, on fine-needle aspiration (FNA) samples, marked cytological atypias are only observed in moderately to poorly differentiated FC, while they may be completely lacking in well differentiated angio- or capsulo-invasive FC. To clarify the cytological features and to improve the accuracy and reliability of aspiration cytology, 892 follicular adenomas and 82 FCs were reviewed. A macrofollicular pattern or large sheet pattern of follicular cells with thin colloid in the background were found to be indicators of follicular adenoma. Crowding or irregular arrangement of follicular cells were found to indicate microfollicular lesions but could not discriminate between benign and malignant conditions. High nucleo-cytoplasmic ratio, nuclear atypia, and coarse granular or dense chromatin were more important criteria for malignancy than nuclear grooves or intranuclear cytoplasmic inclusions. The cytomorphologic features of the follicular neoplasms of the thyroid are described, and the difficulties encountered in the cytodiagnosis of follicular lesions are discussed at length.

Predictive Value of Cytologic Atypia in Indeterminate Thyroid Fine-Needle Aspirate Biopsies

“…These findings may differ from Lubitz et al and Maruta et al who recently looked at cytological features of follicular neoplasms. 15,16 They both reported a correlation between nuclear grooves and inclusions with malignancy but did not identify them as independent predictors factors. Of note, their studies focused on the differentiation of follicular carcinoma from follicular adenoma on cytology and this is the study population for which they selected.…”

A systematic approach to assess the strengths and limitations of cytomorphology in the diagnosis of the follicular variant of papillary thyroid carcinoma

“…For the assessment of nuclear size, perhaps morphometric evaluation would be a better and more objective alternative, although routine cytomorphology is not in any way inferior . Nuclear irregularity has been described by some investigators as a feature of malignancy . However, in our cases, it was attributed to degenerative change.…”

Macrofollicular Variant of Follicular Thyroid Carcinoma: A Case Report

“…Correspondingly, FNAB provides essential information regarding architectural and cytology aspects of the thyroid nodules and plays a key role as a screening test for thyroid follicular neoplasms [4,5]. FTC classically shows microfollicular growth pattern and identification of this component is the key feature in order to classify these nodules as suspicious for a follicular neoplasm, even though the majority (>70 %) of these nodules turn out to be benign on surgical follow-up [4,5]. Thus, cytological specimens of macrofollicular variant of FTC can be a pitfall and be misinterpreted as benign due to the lack of microfollicles [5].…”

“…FTC classically shows microfollicular growth pattern and identification of this component is the key feature in order to classify these nodules as suspicious for a follicular neoplasm, even though the majority (>70 %) of these nodules turn out to be benign on surgical follow-up [4,5]. Thus, cytological specimens of macrofollicular variant of FTC can be a pitfall and be misinterpreted as benign due to the lack of microfollicles [5]. Therefore, they may account for an undetermined fraction of the false-negative FNAB cases.…”