Abstract
Background: Thyroid neoplasms with follicular architecture can have overlapping morphologic features and pose diagnostic confusion amongst pathologists. Various immunohistochemical stains have been investigated as potential diagnostic markers for PTC; amongst which HBME1 and CK19 have gained popularity. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) poses similar diagnostic challenges with interobserver variability and is often misdiagnosed as adenomatoid nodule or follicular adenoma. This study aims to evaluate expression of HBME1 and CK19 in NIFTPs in comparison to other well differentiated thyroid neoplasms and benign mimickers. Method: 73 thyroid cases diagnosed over a period of 3 years at Methodist University Hospital, Memphis, TN were included in this study: 9 NIFTP, 18 papillary thyroid carcinoma (PTC), 11 follicular variant of papillary thyroid carcinoma, invasive (I-FVPTC), 24 follicular adenomas (FA), and 11 multinodular goiters/ adenomatoid nodules (MNG). A tissue microarray (TMA) was constructed and HBME1 and CK19 IHC was performed.Results: HBME1 was expressed in 77.8% NIFTPs, 88.9% PTC, 81.8% I-FVPTC, 16.7 % FA, and 18.2% MNGs. CK19 expression was seen in 66.7% NIFTPs, 83.3% PTC, 81.8% I-FVPTC, 33.3% FA and 45.4% MNGs. Difference in expression of HBME1 and CK19 was statistically significant for NIFTP vs FA (qualitative; p<0.05) and NIFTP vs MNG (p<0.05). No statistically significant difference was found for HBME1 in NIFTP vs PTC (conventional and FVPTC), p>/= 0.2. Sensitivity of HBME1 and CK19 for NIFTP were 78% and 67%, ~88% each for PTC, and 89% and 100% for FVPTC respectively, while specificity of HBME1 and CK19 for NIFTP were 53% each, ~62% each for PTC and ~55% each for FVPTC. Conclusion: Our study indicated that HBME1 and CK19 are valuable markers in differentiating NIFTPs from morphologic mimics like follicular adenoma and adenomatoid nodules/ multinodular goiter. While HBME1 and CK19 are both sensitive in diagnosing lesions with PTC like nuclear features, CK19 stains a higher number of benign lesions in comparison to HBME1. No increase in sensitivity or specificity in diagnosis of NIFTP, PTC or FVPTC was noted on combining the two antibodies.
Impact of Reclassification on Thyroid Nodules with Architectural Atypia: From Non-Invasive Encapsulated Follicular Variant Papillary Thyroid Carcinomas to Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features
