[413] Correlation of “Follicular Lesion” with Final Histopathology of Thyroid Lesions and Comparison to “Follicular Lesion of Undetermined Significance”.

Benjamin Murray, Ping Hou. Washington University Medical Center, St. Louis, MO

Background: In the Bethesda Thyroid Fine-Needle Aspiration (FNA) Classification System, the category of “atypia of undermined significance or follicular lesion of undetermined significance” is appropriate for aspirations with “architectural and/or nuclear atypia that is not sufficient to be classified as suspicious for malignancy or malignancy. A diagnosis of “follicular lesion of undetermined significance (FLUS)” is reserved for aspirates that demonstrate a predominantly microfollicular pattern with minimal or no colloid, sparsely cellular specimens with Hürthle cell predominance, and other indeterminant features. From 2001-2008, Barnes-Jewish Hospital (BJH) used the term “follicular lesion” to describe thyroid aspirates with similar criteria. The objective of this retrospective study was to correlate thyroid lesions with a diagnosis of “follicular lesion” on FNA with histopathology and compare the results to published FLUS estimates for risk of malignancy and usual management.
Design: The study comprises of 512 patients at BJH with FNA diagnosis of “follicular lesion” from 2001-2008. Initial FNA diagnoses with histologic correlation were evaluated. FNA diagnoses of follicular neoplasm and histologic diagnoses of incidental papillary cancer and papillary microcarcinoma, defined as lesions less than 10 mm in greatest diameter, were excluded from the study.
Results: 512 thyroid FNA biopsies were described as “follicular lesion.” Histologic follow-up was available in 279/512 (54.5%). Of these 279 patients, 235 (84.2%) have benign results and 44 (15.8%) have malignant results. The distribution of histopathology findings are summarized in Table 1.

Nodular hyperplasia16860.2
Follicular adenoma6021.5
Follicular variant of papillary carcinoma (FVPTC)279.7
Papillary carcinoma155.4
Follicular carcinoma10.3
Other carcinoma (Insular carcinoma)10.3
Parathyroid adenoma / Hashimoto's thyroiditis72.5

Conclusions: The majority of “follicular lesion” was benign. As our “follicular lesion” showed similar diagnostic criteria to FLUS, these results support the estimated risk of malignancy and the NCI recommendation of repeat FNA for FLUS. While 15.8% of our “follicular lesion” was malignant on histopathology (NCI estimated risk of malignancy is about 5-15%). The most significant proportion of malignant diagnoses was papillary carcinoma, especially FVPTC. It could be a potential pitfall of repeat FNA for this group of patients due to a paucity or lack of well defined nuclear features of FVPTC.
Category: Cytopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 62, Wednesday Afternoon


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