[460] Paired Box Gene 8 (PAX8), HBME-1 and CK19 Expression in Preoperative Fine Needle Aspiration (FNA) of Papillary Thyroid Carcinoma: Diagnostic Utility

AC Schmitt, C Cohen, MT Siddiqui. Emory University Hospital, Atlanta, GA

Background: The diagnosis of papillary thyroid carcinoma (PTC) can be particularly challenging in FNA's with low cellularity. The use of immunohistochemical (IHC) stains, such as HBME1 and CK19, have been extensively studied to increase the diagnostic accuracy of PTC. PAX8, a member of the thyroid-specific transcription factors, has recently been investigated, mostly with molecular techniques, as a useful marker of thyroid epithelial neoplasms. Its utility by IHC in PTC has not yet been well studied. Our goal was to compare the IHC expression of PAX8 with HBME-1 and CK19 expression on cell block preparations from FNA samples with a diagnosis of PTC. To the best of the authors knowledge this is the first study documenting the results of these markers as a panel, in thyroid FNA samples.
Design: 32 cases of PTC diagnosed on FNA were included. The FNA cell blocks were IHC stained for PAX8, HBME-1 and CK19. 10 cases of benign thyroid nodules (BTN) were included as a control group.

Table 1: Immunohistochemical staining results.
PTC31/32 (96.8%)25/32 (78.1%)24/32 (75%)
BTN10/10 (100%)1/10 (10%)1/10 (10%)

Table 2: Sensitivity and Specificity of IHC stains used.

Conclusions: PAX8 demonstrates positivity in a very high number of patients with PTC. However, its positivity in all cases of BTN limits its usage for detecting PTC in FNA samples. HBME-1 had the highest sensitivity and specificity for PTC in our study with CK19 demonstrating a high degree of both sensitivity and specificity for PTC. HBME-1, CK19 and PAX8 may all have a role, particularly as a panel, in detection and diagnosis of PTC. However, PAX8 demonstrates a very low specificity, which may limit its utility in detecting PTC.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 46, Wednesday Afternoon


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