Evaluation of the follicular patterned thyroid lesions based on the WHO 2022 criteria with an emphasis on the grey-zone lesions

Sunayana Misra; Shashi Dhawan; Sonia Badwal; Arupparna Sengupta; Aanchal Khosla; Sangeet Kumar Agarwal; Seema Rao

doi:10.1016/j.anndiagpath.2024.152282

Evaluation of the follicular patterned thyroid lesions based on the WHO 2022 criteria with an emphasis on the grey-zone lesions

Ann Diagn Pathol. 2024 Feb 14:71:152282. doi: 10.1016/j.anndiagpath.2024.152282. Online ahead of print.

Authors

Sunayana Misra¹, Shashi Dhawan¹, Sonia Badwal¹, Arupparna Sengupta¹, Aanchal Khosla¹, Sangeet Kumar Agarwal², Seema Rao³

Affiliations

¹ Department of Pathology, Histopathology Division, Sir Ganga Ram Hospital, New Delhi, India.
² Department of Head and Neck Oncosurgery, Sir Ganga Ram Hospital, New Delhi, India.
³ Department of Pathology, Histopathology Division, Sir Ganga Ram Hospital, New Delhi, India. Electronic address: seemarao1974@yahoo.co.in.

PMID: 38522359
DOI: 10.1016/j.anndiagpath.2024.152282

Abstract

Follicular-patterned thyroid nodules (FPTN) are classified byWHO-2022 into benign, borderline and malignant categories. There are however, grey-zone lesions that pose a diagnostic challenge due to ambiguity in defining criteria and inter-observer variability. WHO-2022 has enumerated specific diagnostic criteria for these lesions. Accurate categorization of morphologically similar TNs is vital to reduce overtreatment of indolent lesions. In this study, we have reclassified FPTNs according to WHO-2022 criteria, emphasizing on grey-zone lesions. We studied the utility of immunohistochemistry (IHC)-CD56, HBME-1 and CK19 in distinguishing benign from malignant nodules and BRAFV600E IHC to better distinguish the (widely-invasive) encapsulated follicular variant of papillary thyroid carcinoma (FVPTC) from infiltrative FVPTC. Only those cases with dominant nodule having follicular pattern histology were included and re-evaluated for following histopathological features-focality, encapsulation, circumscription, nuclear PTC features, capsular-invasion, angio-invasion, papillae and necrosis. IHC findings for above-mentioned markers were noted. Seventy-nine cases met the inclusion criteria. Amendment of original diagnosis was done in 19 % cases. BRAFV600E IHC was positive in the two cases of infiltrative FVPTC while it was negative in all nine IE (invasive encapsulated) FVPTCs. Diffuse HBME1 was noted in most malignant nodules (61 %) while CD56 was expressed more often in benign lesions (70 %). CK19 was positive in lesions displaying nuclear PTC features (86 %). Using WHO 2022 criteria, we were able to re-classify follicular thyroid lesions with greater confidence. Appropriate IHC panel in adjunct to histology aids in categorizing challenging cases.

Keywords: BRAFV600E; FVPTC; Follicular patterned lesions; IEFVPTC; NIFTP; WHO2022 thyroid.