Pancreatoblastoma

Anu Bansal, MD - Case Coordinator
Donnella S Green, MD - Radiology Discussion
Kimberley M Springer, MD - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist

June 9, 2003

Presentation

Imaging Findings

Transverse ultrasound images through the left hepatic lobe show a round, hypoechoic mass (1-2 cm) just below the tip of the lateral segment (within the pancreas). Doppler flow is demonstrated to this mass. Computed tomography images demonstrate that the mass is lower in attenuation than the surrounding pancreatic tissue and is not enhancing. The major vessels are not involved. Both fluid and soft tissue attenuations are present within the lesion. On T1-weighted MRI, the mass is generally iso-intense to the rest of the pancreas (some areas have slightly lower intensity). On T2-weighted images, multiple small, cystic areas are visible. With contrast, peripheral enhancement is evident.

Differential Diagnosis

Diagnosis

Discussion

The spleen and pancreas were resected. The tumor is visible on the right side of the image. The gross evaluation was not instructive. Most of the tumor is necrotic. Histopathology revealed a typical mixture of cells for a pancreatic neoplasm: ductal elements, acinar and neuroendocrine cells. The high power view shows the whiteness that differentiates pancreatoblastoma from other entities. Morphologic and immunophenotypic features (in particular, evidence of mixed acinar, ductal, and endocrine differentiation, "squamoid corpuscles," and focal aberrant nuclear staining for beta-catenin) are characteristic of pancreatoblastoma.

Radiology Discussion:

Pancreatoblastoma is a rare pediatric carcinoma of the pancreas. The majority of these tumors arise in the head of the pancreas. Elevated alpha-fetoprotein may be an indicator of pancreatoblastoma. This is due to the fact that both the liver and the pancreas arise from the same primitive cells, and the regression associated with neoplastic cells is similar in both organs. This tumor is associated with a better prognosis than adult pancreatic carcinoma

Imaging may show a finely calcified mass in the region of the pancreas that may be reminiscent of neuroblastoma. The calcifications are generally not large or formed, as is seen in teratoma. The tumors are often large at diagnosis with hemorrhagic necrosis and degeneration within the tumor. Both solid and cystic elements are typically present. Metastases to liver and lymph nodes are common at diagnosis; lung and brain metastases are rarer.

Pancreatic tumors in children are classified as epithelial (non-endocrine and endocrine) and non-epithelial in origin. Non-epithelial tumors can be subdivided into primary lymphoma, primitive neuroectodermal tumor (PNET) and sarcoma, or metastases; lymphoma is the most common type. Benign non-endocrine tumors are very rare and include adenomas and dermoid cysts (teratoma). Malignant non-endocrine lesions include pancreatoblastoma and papillary carcinoma. The most common endocrine lesion is nesidioblastosis; insulinoma is much more rare. The most common cystic pancreatic neoplasms in children are microcystic adenomas and cystadenocarcinomas. Their appearance is similar to that in adults. They may cause a pseudomyxoma peritonei if they rupture into the peritoneum.

References

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