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Pancreas

Exocrine tumors

Pancreatoblastoma


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 26 November 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Most common pancreatic tumor of infancy / early childhood, characterized by acinar differentiation, squamoid corpuscles, stromal bands (WHO)

Clinical features
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● Children: 50% cured after excision; most survive and do well with chemotherapy if no metastases, but those with metastases often die
● Children: higher survival if complete resection; 5 year overall survival is 79% (Eur J Cancer 2011;47:2347)
● Adults: mean survival 18 months

Case reports
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● 27 year old woman with breast, liver and lung metastases (JOP 2012;13:301)

Gross description
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● Partially encapsulated, often lobulated, mean 10 cm

Gross images
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Lobulated surface


Encapsulated tumor with nodular surface


Encapsulated heterogeneous mass with cystic components filled with serous fluid

Micro description
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● Mixtures of acini, squamoid corpuscles and less commonly endocrine or ductal features
● Very cellular, uniform epithelial cells in sheets and nests with acini/ducts
● Squamoid corpuscles (circumscribed whorled nests of plump spindle cells with a squamous appearance and occasional keratinization) are common and specific; note: this indicates a growth pattern, not a line of differentiation
● Pediatric cases often have hypercellular stroma, occasionally with bone/cartilage

Micro images
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Squamoid nests


36 year old woman: cords of primitive small cells differentiating into squamoid nests with central keratinization, with (left) and without (right) calcification


Tumor cells grow in acinar pattern and include groups of cells with pale cytoplasm ("squamoid corpuscles")


Mixed solid-glandular pattern


Solid tumor with scattered squamoid corpuscles


Nests of squamous or epidermoid tissue in a background of small, diffusely infiltrating cells


Various images


Spindle cells with sarcomatoid features


Chondroid tissue surrounded by spindle cells


Spindle cells (center), epithelial cells (right), and osteoid (left)


Metastases to liver: acinar pattern with squamous morule


CAM5.2+ tumor cells in acinar pattern; squamoid corpuscles do not stain


Various immunostains

Cytology description
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● Cellular smears with both epithelioid (acinar or undifferentiated) and immature mesenchymal cells (Arch Pathol Lab Med 2009;133:388)

Positive stains
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Note: presence of optically clear nuclei may cause false positive immunohistochemical staining with ABC (biotin) technique
● Pancreatic enzymes in acinar areas, CEA and mucin in luminal secretions of small acini
● Also keratin, alpha-fetoprotein (18%), aberrant (nuclear/cytoplasmic) expression of beta-catenin in squamous morules

Negative stains
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● Neuroendocrine markers (rare cells may be positive)

Electron microscopy description
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● Acinar cell features

Differential diagnosis
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Acinar cell carcinoma: no squamous corpuscles
Solid pseudopapillary neoplasm: pseudopapillae with hyalinized fibrovascular cores lined by several layers of bland fragile epithelial cells with clear to eosinophilic cytoplasm

End of Pancreas > Exocrine tumors > Pancreatoblastoma


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