[433] Utility of Islet-1, CD99, PAX8 and β-Catenin in Fine Needle Aspiration Workup of Non-Ductal Pancreatic Neoplasms

Claudia Velosa, Jacqueline Nunez, Jan F Silverman. Allegheny General Hospital, Pittsburgh, PA

Background: Endoscopic ultrasound guided fine-needle aspiration (FNA) is a useful method for the diagnosis of pancreatic neoplasms, including pancreatic endocrine neoplasms (PEN), acinar cell carcinoma (ACC), solid-pseudopapillary neoplasm (SPN) and ductal adenocarcinoma (DA). However, the cytologic diagnosis of the non-ductal neoplasms can occasionally be challenging due to overlapping diagnostic features. We evaluated a panel of antibodies to determine which markers could provide the best immunophenotypic characterization for problematic cases of PEN, ACC and SPN on FNA cytology.
Design: 37 cases of FNA of pancreatic neoplasia were selected. Cell blocks from 16 PEN, 6 SPN and 3 ACC and 12 DA were immunohistochemically (IHC) stained for PAX8, CD99, b-catenin, CD10, Islet 1, DOG1, synaptophysin (Sy), chromogranin (Ch), a1-antitrypsin (AT), a1-chymotrypsin (ACT). The slides were independently scored by two investigators as negative (<5% positivity) or positive (>5% moderate strong positivity).
Results: PEN showed strong nuclear staining for PAX 8 in 14/16 (87.5%) cases and Islet 1 in 13/16 (81.2%) cases. Membranous staining for CD99 was present in 12/16 (75.0%) of PEN. All cases of PEN were positive for Sy and Ch and negative for CD10, DOG1, b-catenin, AT and ACT. Strong nuclear staining for b-catenin was present in all cases of SPN. 5/6 (83.3%) of SPN showed perinuclear dot staining for CD99 and 4/6 (66.6 %) cases were positive for CD10. 2/6 (33.0%) of SPN showed coexpression of Sy and Ch and PAX8 was positive in 2/6 (33.3%) of SPN. 1 SPN showed coexpression of the three markers and 1/6 (16.6%) SPN showed staining for AT. There was no expression of DOG-1 in SPN. All cases of ACC showed positive staining for AT and ACT. 1 case of ACC coexpressed CD10, Sy and Ch. DOG-1 was the only positive staining in DA, in 2/12 (16.6%) cases.
Conclusions: 1. SPN, PEN and ACC showed overlapping of immunophenotypic patterns, especially for neuroendocrine markers.
2. In differentiating SPN from PEN, β-catenin and CD99 (perinuclear dot staining) expression was highly specific (100/100%, respectively) and sensitive (100%/ 83%, respectively) for SPN.
3. Islet 1 was the most specific (100%) marker for PEN. Although PAX-8 was highly sensitive (87.5%) for PEN, it was less specific (90%) than Islet-1, since it was also present in 33% of SPN.
4. AT expression was highly sensitive (100%) for ACC, but less specific (97%) since it also stained 16% of SPN, but no PEN.
5. We recommend β-catenin, CD99, PAX8 and Islet 1 to be included in the IHC panel for the FNA cytology work-up of non-ductal pancreatic neoplasms.
Category: Cytopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 75, Tuesday Afternoon


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