Solid Pseudopapillary Tumor of Pancreas

Matthew P Schenker, MD - Case Coordinator
Matthew P Schenker, MD - Radiology Discussion
Michael W Bennett, MB, BCH - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist

April 28, 2003

Presentation

Imaging Findings

The chest radiograph does not show any focal abnormalities. On bone windows, curvilinear calcification is visible in the left upper quadrant of the abdomen. Axial contrast-enhanced CT images show many enlarged vessels around the stomach. In the region of the pancreatic body/tail, there is a large, low-density cystic lesion with peripheral calcification. To the left side of the low-density lesion there is a heterogeneous, lobular soft tissue density with central, punctate calcifications.

Differential Diagnosis

Diagnosis

Discussion

The gross sample is a distal pancreatectomy and splenectomy. There is a large (9.5 cm) mass near the pancreatic resection margin. On cross section, the mass has cystic and fibrotic areas as well as calcifications and focal hemorrhage. Low-power microscopy shows a solid area, the capsule, and normal pancreas. High-power microscopy from a different area shows pseudo-papillae around stromal nodules. The main characteristic of this tumor is that the epithelial cells seem to be falling away and undergoing mitosis. Immunohistochemistry confirmed the diagnosis (beta-catenin positive).

The pancreatic resection margin was negative for tumor, but the tumor did extend to the soft tissue resection margin. Lymphovascular invasion was identified, but nine of nine pancreatic lymph nodes were free of tumor, as were two splenic hilar lymph nodes. The spleen was not involved.

Radiology Discussion:

Pancreatic tumors can be categorized as endocrine and exocrine tumors. These categories can be further broken down into solid or cystic epithelial (exocrine) and non-functional and functional (endocrine). Cystic epithelial tumors include serous cystic, mucinous cystic, intraductal papillary mucinous, and solid pseudopapillary tumors.

Solid pseudopapillary tumor is also known as a solid-cystic, papillary-cystic, or solid and papillary (epithelial) neoplasm. It is typically benign but may be a low-grade malignancy. These tumors can occur in any part of the pancreas. The incidence is higher in women and these tumors tend to strike relatively young people, with a peak in the second and third decades. Solid pseudopapillary tumors tend to be large (3-18 cm). On gross inspection, there is a thick, fibrous capsule surrounding a solitary, solid to cystic mass (hence the prior terms of solid-cystic tumor). There are typically finger-like projections of tissue of pseudopapillary excresences. Microscopy demonstrates a solid periphery and a pseudopapillary center. As the tumors increase in size, the cystic components—as well as areas of hemorrhage and necrosis—also increase. Ultrasound imaging reveals a solid, hypoechoic, well-circumscribed mass. On CT and MR, the tumor appears heterogeneous (centrally variable) with a thick, enhancing capsule. Papillary projections and hemorrhage may be evident on these modalities.

Serous cystic tumors are also known as microcystic adenoma, serous cystadenoma or cystadenocarcinoma. They are generally benign and occur more often in women than in men (1.5-4:1). Unlike solid pseudopapillary tumors, serous cystic tumors strike older patients, with an average age of 60-70 years. This large (10-13 cm) tumor can occur in any area of the pancreas. On gross examination, it is a spongy, well-cicrumscribed, lobular mass with multiloculated cysts. Microscopy reveals multiple small (<2 cm) cysts containing glycogen-rich fluid, hypervascularity, thin septae and a central stellate calcified scar. On ultrasound, serous cystic tumors are solid lesions with an echogenic central stellate scar. On CT, it is a well-defined, low-attenuation mass that shows marked enhancement; it often has a "honeycomb" appearance. On MR, the signal is low dues to the central scar. The mass is hyperintense on T2-weighted images and bright on T1 when areas of hemorrhage are present.

Mucinous cystic tumors are also known as cystadenoma, cystadenocarcinoma, or macrocystic adenoma. They range from benign to frankly malignant and show a strong female predominance (8-9:1). The average age at presentation is 40-60 years. Mucinous cystic tumors occur most often in the tail or body of the pancreas, but can also occur in the pancreatic head. The size is variable, but the cysts contained within the tumor can be large (up to 5 cm). Grossly, the tumor may be either multilocular or unilocular, mimicking a pseudocyst. On microscopy, the tumor is shown to contain cysts >2 cm with a large amount of mucin. The walls are 1-2 mm thick, and the mass is hypovascular. Solid papillary excrescences are visible. On ultrasound, the lesion has internal spetations and papillary projections. Ductal dilatation may be evident. On CT, the mass is hypovascular. The walls and septations enhance with contrast. The appearance on MR is variable and depends upon the material within the cysts (e.g., protein, blood).

Intraductal papillary mucinous tumor (IPMT) is also known as mucin-producing tumor, intraductal mucin hypersecreting neoplasm, mucin hypersecreting tumor, mucinous ductal ectasia or ductectatic mucinous cystic tumor. This is a relatively newly reported entity. It is a soft, villous tumor typically associated with Wirsung’s duct and branches. It is characterized by papillary projections lined by columnar mucin-secreting cells with varying degrees of cellular atypia. The main imaging characteristic is the dilation of the main pancreatic duct, which may or may not be accompanied by a visible cystic lesion.

References

Dong PR, Lu DSK, Degregario F, Fell SC, Au A, Kadell BM: Solid and papillary neoplasm of the pancreas: radiological-pathological study of five cases and review of the literature. Clin Radiol, 1996, 51: 701-705.

Mergo PJ, Helmberger TK, Buetow PC, Helmberger RC, Ros PR: Pancreatic neoplasms: MR Imaging and pathologic correlation. Radiographics, 1997, 17: 281-301.

Choi BI, Kim KW, Han MC, Kim YI, Kim CW: Solid and papillary epithelial neoplasms of the pancreas: CT findings. Radiology, 1988, 166: 413-416.

Ros PR, Mortelé KJ: Imaging features of pancreatic neoplasms. JBR-BTR, 2001:84:239-49.

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