Pancreas - Solid pseudopapillary tumor of pancreas

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Pancreas

Exocrine tumors

Solid pseudopapillary tumor of pancreas

Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 3 December 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Low grade malignancy composed of poorly cohesive monomorphic epithelial cells forming solid and pseudopapillary structures (WHO)
● Not truly papillary or truly cystic
● Also called SPT, papillary and solid epithelial neoplasm, papillary cystic neoplasm, Gruber-Frantz tumor
● 1-2% of non-endocrine pancreatic neoplasms
● Mean age 30-35 years, 90% women, not associated with any clinical syndrome

Etiology
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● May be unique to pancreas (Mod Pathol 2007;20:S71)
● May derive from centroacinar cells due to DOG1 immunoreactivity in both (Hum Pathol 2011;42:817)
● Discohesive nature of cells and cystic changes may be due to abnormalities in expression of E-cadherin/catenin complex (Am J Surg Pathol 2008;32:1)

Poor prognostic factors
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● Venous invasion, high nuclear grade, “necrobiotic nests”
● Metastases in 10-15% to liver or peritoneum are associated with venous invasion, high nuclear grade and necrosis
● Patients usually survive even with metastases

Case reports
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● 33 year old woman with large, multilocular cystic mass (Case of the Week #121)
● 38 year old woman with liver metastases (Arch Pathol Lab Med 1995;119:268)
● 43 year old woman with retroperitoneal mass (Arch Pathol Lab Med 2001;125:971)
● 44 year old woman with pancreatic mass (Arch Pathol Lab Med 2002;126:985)
● Papillary cystic tumor of the pancreas (Arch Pathol Lab Med 1984;108:723)

Treatment
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● Wide excision, excellent prognosis (J Surg Oncol 2007;95:304)

Clinical images
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CT scan

Gross description
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● Large (mean 9 cm), usually encapsulated, hemorrhagic, necrotic, rarely multifocal (Arch Pathol Lab Med 1991;115:958)
● Tumor friable but not necrotic

Gross images
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Lobulated, fleshy surface showing marked hemorrhage and degenerative changes

Solid and cystic masses

Multilocular cystic mass

Whipple specimen showing large, round, well-demarcated mass in head of pancreas; tumor is partly necrotic and cystic (Courtesy of Dr. Andreas Schulz, Giessen, Germany)

Tumor invades spleen, and gave rise to liver metastases (Courtesy of Dr. Manfred Stolte, Bayreuth, Germany)

Cut surface shows uniloculated cyst with some solid areas in capsule (Courtesy of Dr. Helmut Luchtrath, Koblenz, Germany)

Micro description
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● Cellular tumor, resembles pancreatic endocrine neoplasm or CNS ependymoma
● Pseudopapillae with hyalinized fibrovascular cores lined by several layers of bland fragile epithelial cells with clear to eosinophilic cytoplasm, variable mucinous changes within the core, intracytoplasmic PAS+ hyaline globules
● Pseudopapillae are due to solid nests minus cells degenerating away from the small vessels; resemble rosettes in cross section
● Also round/oval nuclei, finely stippled chromatin, nuclear grooves, indistinct nucleoli, few mitoses
● Also foam cells, clusters of lipid/cholesterol crystals surrounded by foreign-body giant cells
● May have pseudocystic areas
● Tumor cells infiltrate without any stromal reaction

Micro images
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Pseudopapillae

Tumor cells radially arranged around delicate and somewhat hyalinized fibrovascular stalk; arrows point to small hyaline globules within and between the cells

Hyaline globules (hematoxylin phloxine saffron stain)

Solid monomorphous pattern with variable vacuoles and sclerosis

Nuclei lack conspicuous nucleolus but show indentations

Solid part of tumor has aggregate of large tumor cells with foamy cytoplasm (arrows); arrowheads point to small cyst filled with eosinophilic fluid and some foam cells

Cholesterol crystals surrounded by foreign body cells

Tumor tissue (top) is sharply demarcated from adjoining pancreatic parenchyma (bottom), but lacks a clear capsule

Margin of a malignant tumor with deep invasion into the adjacent pancreatic tissue

Aggressive histologic features

Case of the Week #121

Various images

Left to right: CD10+, CD56+, Vimentin+

Left to right: E-cadherin, β-catenin

Left to right: PR+, alpha-1-antitrypsin+, βcatenin

Intense focal immunostaining for alpha-1-antitrypsin

Diffuse immunostaining for NSE

Cytology description
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● Cellular, single cells, small loose clusters, and scattered intact papillary structures with delicate fibrovascular cores, fibrovascular cores may contain metachromatic material, and hyaline globules may be seen extracellularly, cells have delicate, finely granular cytoplasm (Korean J Pathol 2012;46:399)
● Chromatin is fine and nuclei are frequently grooved

Cytology images
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Branching vessels and cohesive cells

Various images

Comparison with pancreatic neuroendocrine tumors

Immunostains

Positive stains
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● Vimentin, CD10, CD56 (intense, diffuse, Am J Surg Pathol 2000;24:1361)
● Intense membranous claudin 5 and cytoplasmic claudin 2 (Am J Surg Pathol 2009;33:768, Hum Pathol 2008;39:251)
● Also estrogen and progesterone receptors, focal neuroendocrine markers
● Also chymotrypsin and trypsin (Am J Surg Pathol 1987;11:85)
● Also nuclear and cytoplasmic beta-catenin (Am J Clin Pathol 2009;132:831), cyclin D1, nuclear E-cadherin, paranuclear dot like CD99 (Am J Surg Pathol 2011;35:799),

Negative stains
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● Chromogranin, CEA, acinar and ductal markers (keratin may be patchy)

Electron microscopy description
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● Large electron dense granules with complex internal membranous and granular inclusions and alpha-1-antitrypsin

Electron microscopy images
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Tumor cells with abundant cytoplasm containing multiple mitochondria and a few dense bodies; nuclei have a polygonal shape (Courtesy of Dr. H.D. John, Mainz, Germany)

Large osmiophilic, zymogen-like granules of variable sizes; often is disintegration of granule content, forming multilamellated vesicles (Courtesy of Dr. H.D. John, Mainz, Germany)

Molecular description
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● Almost always mutations in exon 3 of the beta-catenin gene, causes abnormal immunostaining patterns for beta-catenin (nuclear and cytoplasmic, compared to membranous staining in normal pancreas) and overexpression of cyclin D1 (Am J Pathol 2002;160:1361)

Differential diagnosis
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● Acinar cell carcinoma: typically has acinar formations, prominent nucleoli and mitotic activity, trypsin+, chymotrypsin+, lipase+ (Mod Pathol 2007;20:S94)
● Adrenal cortical tumors: positive for inhibin, keratin
● Pancreatic endocrine tumor: no degenerative pseudopapillae, no clear cells, usually no intracytoplasmic hyaline globules, no longitudinal nuclear grooves; no nuclear β-catenin staining, CD10- (Am J Surg Pathol 2011;35:981)
● Pancreatic pseudocyst: may be grossly similar, but no epithelial cells lining the cystic structures, even after careful search, patients are usually older and male, and have a history of pancreatitis)

End of Pancreas > Exocrine tumors > Solid pseudopapillary tumor of pancreas

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