[1567] Hyaline Globules in Neuroendocrine and Solid-Pseudopapillary Neoplasms of the Pancreas: A Clue to the Diagnosis.

Zina Meriden, Chanjuan Shi, Barish Edil, Trevor Ellison, Christopher Wolfgang, Richard Schulick, Ralph H Hruban. The Johns Hopkins University School of Medicine, Baltimore, MD

Background: Distinguishing between solid pseudopapillary neoplasm (SPN) and pancreatic neuroendocrine tumors (PanNET) can be problematic. Both can have solid growth patterns, and immunolabel with antibodies to endocrine markers such as synaptophysin and CD56. One established feature of SPN is the presence of hyaline globules.
Design: All available histologic slides from 361 cases originally diagnosed as PanNET were reviewed. Of these, 24 cases had hyaline globules, raising the possibility of SPN. Immunolabeling studies for synaptophysin and beta-catenin were performed on the 24 cases with hyaline globules, and CD10 was used as a confirmatory test in cases with nuclear beta-catenin. PAS, PAS with diastase, and immunolabeling with alpha-1-antitrypsin and trypsin were performed to characterize the hyaline globules. All 24 cases were examined for the pattern of invasion, microcystic change, hemorrhage, cholesterol clefts, clear cells, foam cells, nuclear grooves, and foci of discohesion.
Results: 6 of the 24 cases with hyaline globules had nuclear labeling for beta-catenin, expressed CD10, and were reclassified as SPN. The remaining 18 cases maintained their original diagnosis as PanNET. A subset of these 18 cases had only focal hyaline globules which were absent on deeper levels. Hyaline globules were PAS-positive, diastase resistant (16/16 evaluable cases), and immunolabeled with alpha-1-antitrypsin (12/15 cases) or trypsin (1/16 cases). The mean age of the 24 patients was 54 years, 56 for patients with PanNET, and 48 for patients with SPN. There was no difference in patient gender (SPN: 50% male vs. PanNET: 55.6% male, P=1). When the 24 cases with hyaline globules were compared, 3 features suggestive of SPN emerged: an insidious pattern of invasion wherein normal pancreatic elements are entrapped by the tumor (83.3% SPN vs. 11.1 % PanNET, P=0.003), clear cells (100% SPN vs. 27.8% PanNET, P=0.003), and nuclear grooves (50% SPN vs. 0% PanNET, P=0.010).
Conclusions: The morphologic features of SPN and PanNET overlap. Small SPNs with minimal degenerative changes are particularly hard to recognize. In these cases hyaline globules should raise SPN in the differential diagnosis, and the diagnosis can be established with immunolabeling for beta-catenin. Additionally, the presence of hyaline globules should not be used as a sole diagnostic criterion for SPN, as 5% of PanNETs contain hyaline globules. Features supporting the diagnosis of SPN include nuclear beta-catenin labeling and CD10 expression, an insidious pattern of invasion, clear cells, and nuclear grooves.
Category: Liver & Pancreas

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 218, Tuesday Afternoon


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