Observer Variation of Encapsulated Follicular Lesions of the Thyroid Gland

Abstract

Although histologic definition of follicular thyroid lesions is readily available, application of the diagnostic criteria and personal experience may lead to disagreement among pathologists. To investigate interobserver variation in assessment of encapsulated follicular lesions, eight pathologists (four American and four Japanese) reviewed the same hematoxylin and eosin-stained slide of each of 21 cases of thyroid lesions showing encapsulation and follicular growth pattern. In 10% of the cases, there was complete agreement. At least seven pathologists agreed on the diagnosis in 29% of the cases, and at least six in 76% of the cases. American and Japanese pathologists agreed among themselves in 33% and 52% of cases, respectively. The frequency of diagnosis of adenomatous goiter among Japanese pathologists (31%) was considerably higher than that among American pathologists (6%). In contrast, the frequency of diagnosis (25%) of papillary carcinoma among American pathologists was considerably higher than that (4%) among Japanese pathologists. Our analysis revealed three main factors affecting observer variation: 1) interpretation of the significance of microfollicles intimately related to capillaries within the tumor capsule, 2) evaluation of what constituted the type of nuclear clearing indicative of papillary carcinoma, and 3) absence of clear morphologic criteria for separation of adenomatous goiter and follicular adenoma. To reduce observer variation of encapsulated follicular lesions, it will be necessary to provide more explicit criteria for diagnosis.

Diagnostic value of TROP-2 expression in papillary thyroid carcinoma and comparison with HBME-1, galectin-3 and cytokeratin 19

“…However, it is known that there are disagreements among even endocrine pathologists analyzing the same lesion, in suspicious thyroid nodules [2]. Factors that affect the variety among observers include education of pathologists in different centers and by different educators [19]. As far as we observed in consultations made to our department, even distinguish- ing benign thyroid lesions with papillary growth pattern (hyperplastic nodule, hyperfunctioning adenoma, Graves' disease, etc.)…”

Galectin-3, fibronectin-1, CITED-1, HBME1 and cytokeratin-19 immunohistochemistry is useful for the differential diagnosis of thyroid tumors

“…One of the most frequent difficulties in thyroid pathology is differentiating adenomas from carcinomas, especially those with follicular architecture, for example, follicular variant of papillary thyroid carcinoma, follicular and Hü rthle cell carcinomas. 2,4 This differentiation is critical for the treatment and long-term management of the tumors. We found that all five markers were highly specific for carcinoma, but GAL3 was the most sensitive and accurate.…”

“…A more recent study compared the diagnoses of 21 follicular nodules by four American and four Japanese pathologists and showed an agreement of benign vs malignant in only 62% of the nodules. 2 A review of 200 thyroid tumors by seven Italian pathologists revealed good agreement for papillary and anaplastic thyroid carcinomas, moderate for medullary and poor for follicular thyroid carcinomas. 3 In another review of 41 follicular carcinomas by five experienced French thyroid pathologists, the agreement for malignancy varied from 5% among all five pathologists to 56% between two pathologists.…”

Microarray analysis refines classification of non-medullary thyroid tumours of uncertain malignancy

“…However, for decades, conventional histology failed to classify some encapsulated follicular thyroid tumours as benign or malignant because these lesions share overlapping histological features. This already known difficulty is underscored by recent substantial interobserver variability (Hirokawa et al, 2002;Franc et al, 2003;Lloyd et al, 2004), either in the pathological assessment of thyroid nodules or in the identification of underlying diagnosis criteria, such as papillary nuclear features, vascular and/or capsular invasion. These difficulties are especially relevant in encapsulated differentiated thyroid carcinomas for their belonging to the encapsulated follicular variant of papillary thyroid carcinoma (FVPTC) or the minimally invasive FTC group, and for their ability to harbour predominant oncocytic features.…”