Analyzing the ‘Gray Zone’ in Follicular Lesions of Thyroid

Abstract

BACKGROUND: Fine needle aspiration (FNA) is used as a gold standard for diagnosis of thyroid nodules. But, diagnostic efficacy of FNA declines sharply when follicular patterned lesions of thyroid are considered. Hence these lesions form a "gray zone" where a definite diagnosis on FNA is difficult. This article discusses the umbrella diagnosis of 'follicular lesions' on cytology, which largely comprises of four entities i.e., adenomatous goiter, follicular adenoma, follicular carcinoma, and the follicular variant of papillary thyroid carcinoma. AIMS: To assess the accuracy of FNAC in differentiating benign and malignant follicular patterned lesions so as to contribute to better patient care. MATERIALS AND METHODS: A retrospective analysis was conducted between 2009 and 2014 at our institution. Sixty two cases with diagnosis of 'follicular lesion' and 'follicular lesion with atypical cells' on FNA were included in the study. The cytological features were correlated with histopathology and the results tabulated. RESULTS: Sixty two cases with a FNA diagnosis of 'follicular lesion' or 'follicular lesion with atypical cells' was analyzed in the present study. The diagnosis of 'Follicular lesion' was noted in 46 cases and 'follicular lesion with atypical cells' in 16 cases. The histopathology diagnosis was adenomatous goiter in 35 cases, follicular adenoma in 16 cases, follicular carcinoma in four cases, and follicular variant of papillary carcinoma of thyroid (PTC) in seven cases. The malignancy rate in follicular pattern lesions (N=62) was 17.7% and neoplasia rate was 43.5%. In atypical or suspicious cases (N=16) the malignancy rate was 43.7% and the neoplasia rate was 68.7%. CONCLUSION: Follicular-patterned thyroid lesions remain a 'gray zone' and a challenge for cytopathologist. High malignancy rate in these patients supports the concept of giving an umbrella diagnosis of "follicular lesion" and advising excision of the nodule for histopathology to confirm the diagnosis or maintain close follow up.

Diagnostic accuracy of fine needle aspiration cytology of thyroid and evaluation of discordant cases

“…Use of various terms, including ''atypical,'' indeterminate, favor, cannot exclude, possible, or probable and suspicious by pathologists often creates confusion for the clinicians [33]. It is truly a gray zone in thyroid cytology [16,17]. We report these lesions as 'follicular pattern lesions' and advice excision of the lesion followed by HPE for confirmation.…”

“…'Follicular pattern lesion' forms a 'gray zone' in cytology and it is difficult to rule out malignancy on cytology in these lesions [16,17] We report these lesions as 'follicular pattern lesions' and advice excision of the lesion followed by HPE for confirmation.…”