Benign follicular thyroid lesions versus follicular variant of papillary carcinoma: differentiation by architectural pattern

Abstract

Differentiation between benign and malignant follicular lesions is one of the difficult diagnostic areas in thyroid fine needle aspiration (FNA). Nuclear criteria are usually used to distinguish between them. In this study the microarchitectural pattern of common benign follicular lesions, namely nodular hyperplasia (NH) and follicular adenoma (FA) were analysed in comparison with those of follicular variant of papillary carcinoma (FVPC) in order to aid in their differentiation. The FNA smears of histologically proven cases of FVPC, NH and FA were reviewed and compared. The microarchitectural features of FVPC, NH and FA were described. Three cytological features--multi-layered rosettes, branching monolayered sheets and balls of thick pinkish colloid--were exclusively observed in FVPC. Hyperplastic papillae with intact follicles and colloid were frequently seen in NH, 83% and 100%, respectively. Albeit less frequently, they were also noted in FVPC, 25% and 75% of cases, respectively. These overlapping features make the distinction between FVPC and NH sometimes difficult; however, assessing the smears for the specific features of FVPC may help in their differentiation. None of the aforementioned microscopic findings with the exception of the seldom presence of colloid were documented in FA. The crowded clusters of follicular cells were seen both in FA and FVPC; however, they were complex and branching in the latter and round to oval in the former. Finally, smears with good recovery of material are indispensable for the identification of these helpful microarchitectural patterns.

Classical and Follicular Variant Papillary Thyroid Carcinoma: Comparison of Clinical, Ultrasonographical, Cytological, and Histopathological Features in 444 Patients

“…However, diagnostic value of FNAB in FVPTC is limited. Most of the studies show low sensitivities ranging from 9.8% to 37% which are quite low when compared to PTC [27,28]. However, Tielens et al found sensitivity of FNAB in FVPTC as 75% and in PTC as 82% [17].…”

Diagnostic terminology and morphologic criteria for cytologic diagnosis of thyroid lesions: A synopsis of the National Cancer Institute Thyroid Fine‐Needle Aspiration State of the Science Conference

“…Cytoplasmic eosinophilia has been reported in cases of FVPTC. 49,51,63,64,71,73,74,76,77,79,114,146 It has been suggested that if a thyroid FNA specimen focally shows cells with nuclear elongation, chromatin clearing, and grooves but lacks nuclear inclusions, it may be diagnosed such as ''follicular derived neoplasm with features suspicious for PTC.'' In a review of these cases, up to 70% reported as suspicious for PTC category turned out to be follicular variant of papillary carcinoma.…”

Differential Diagnosis of Small Single Solid Thyroid Nodules using Real-Time Ultrasound Elastography

“…The stiffness of malignant thyroid tumours is harder than benign tumours because thyroid follicular adenomas comprise many follicles. 19 These contain abundant pectin, which renders tissue slightly softer in comparison with papillary thyroid carcinomas, which comprise abundant fibrous vascular mesenchyma in the centre with calcified bodies. 20 Real-time USE was useful in the differential diagnosis of these smaller nodules, and could assist in the detection of PTMCs.…”