[584] The Utility of Cyclin D1 in Distinguishing Encapsulated Follicular Variant of Papillary Thyroid Carcinoma from Follicular Adenoma

Denyo Adjoa Zakhia, Wamidh Adwar, Ziying Zhang, Osama Alassi. Henry Ford Health System, Detroit, MI

Background: Distinguishing encapsulated follicular variant of papillary carcinoma (E-FVPC) from follicular adenoma (FA) depends on the classic nuclear features of papillary carcinoma. These features are subjective and dependant on fixation and tissue processing. There is significant interobserver variability among pathologists distinguishing these lesions. In this study, we investigated whether cyclin D1 IHC has a diagnostic value for discriminating E-FVPC from FA.
Design: 23 E-FVPC and 18 FA were stained by IHC for Cyclin D1. All cases of carcinoma were reviewed by two pathologists. Two FA were excluded due to presence of atypical features suspicious for E-FVPC. Staining intensity was graded as negative (0), weak (1+), moderate (2+) or strong (3+). Stain distribution was negative (0%); 1+ (<25%); 2+ (25-75%) or 3+ (>75%) of tumor cells. Mann-Whitney U test was used for statistical analysis.
Results: E-FVPC expressed Cyclin D-1 strongly in 22/23 (96%) of cases (3+ in 70%, 2+ in 26%). Cyclin D1 distribution was 3+ in 74% and 2+ in 22% of E-FVPC. One case (4%) of E-FVPC showed only 1+ intensity and 1+ distribution of cyclin D1. Cyclin D-1 was expressed strongly in 9/18 (50%) of FA (3+ in 11%, 2+ in 39%). Four of the FA with 3+ and 2+ intensity had oncocytic metaplasia and one FA with strong intensity (5.5%) had a background of Hashimoto thyroiditis. Cyclin D1 distribution was diffuse in 8/18 (44%) FA (3+ in 22%, 2+ 22%). 9/18 (50%) FA showed a 1+ staining distribution. A statistically significant association was found between tumor type and cyclin D1 staining distribution and intensity. There were fewer cyclin D1-positive FA than E-FVPC (39% vs. 96%, respectively; p<0.001). Stain distribution was greater in E-FVPC than in FA (96% vs. 44%, respectively; p=0.001).
Conclusions: Cyclin D-1 is a useful marker in distinguishing E-FVPC from FA when there is strong and diffuse staining. Almost all E-FVPC show strong, diffuse staining, however, this marker is not helpful if the adenoma shows oncocytic metaplasia/ changes or there is Hashimoto's thyroiditis. Cases diagnosed as FA may require a review by a second pathologist to exclude the possibility of E-FVPC.
Category: Endocrine

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 35, Wednesday Afternoon


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