Figure 1: The pancreas is enlarged in size and demonstrates diffuse involvement of the pancreatic head and body by cystic lesions. There are two complex cystic and septated pancreatic masses. The uncinate process lesion measures 4.0 x 3.3 x 3.5 cm and the main duct lesion measures a maximum diameter of 1.9 cm. The gallbladder is slightly distended.

Figure 2: Axial image again demonstrates cystic masses involving the pancreatic head and body with multiple internal septations and apparent involvement of the entire pancreatic duct.

Diffuse pancreatic iIntraductal papillary mucinous tumor (IPMT).

Intraductal papillary mucinous tumor (IPMT) of the pancreas is a mucin-producing tumor which arises from the epithelial lining of the pancreatic ducts. The dysplastic epithelium proliferates and forms papillary projections that protrude into and expand the main pancreatic ducts and/or side branch ducts. Duct obstruction is secondary to plugs of mucin elaborated by the epithelium or ductal compression by cystic masses.

The average age at diagnosis is 65 years (range 30-94 years) with a female predominance. The etiology and risk factors are unknown. IPMT can be benign or malignant according to its pathological features, including benign hyperplasia adenoma, borderline low grade dysplasia adenoma, high grade dysplasia adenoma (carcinoma in situ), and malignant adenocarcinoma. Differential diagnosis of IPMT of the pancreas includes chronic pancreatitis, mucinous cystadenoma, cystadenocarcinoma, serous cystadenoma, and pancreatic pseudocyst. Clinical symptoms and signs of IPMT include pancreatitis-like abdominal pain, diarrhea/steatorrhea, and obstructive jaundice, which are caused by thick mucinous ductual obstruction, and diabetes mellitus. Predictive signs of malignancy of IPMT are presence of diabetes mellitus, male gender, marked and diffuse dilatation of main pancreatic duct (>10mm), presence of large mural nodules (> 10 mm), and tumor arising from the head of the pancreas.

IPMTs may be classified into main duct, branch duct, or combined types. Main pancreatic duct type involvement presents as diffuse or segmental ductal dilatation, copious mucin production, papillary growth, and is typically associated with malignancy. These tumors exhibit a greatly expanded main pancreatic duct ranging from 3-10 cm and this severe ductal dilatation is easily mistaken as cystic neoplasm. Branch duct type IPMT predominantly involves the side branch ducts and appear as oval-shaped cystic masses in proximity to the main pancreatic duct. These benign tumors appear as localized cystic parenchymal lesions. The majority of branch duct type IPMTs are located in the uncinate process of the pancreas. The combined type IPMT involves both the main and branch ducts, as in this case.

The following findings are seen on imaging studies: lobulated multicystic dilatation of the branch ducts, diffuse dilatation of the main pancreatic duct, intraductal papillary tumors, elongated or glob-like mucous plugs in the dilated ducts, and bulging of the papilla into the duodenal lumen. The diagnosis of IPMT can be suggested using ultrasonography, CT, or magnetic resonance colangiopancreatography (MRCP). Endoscopic retrograde cholangiopancreatography (ERCP) has traditionally been the imaging modality of choice for diagnosis because it depicts the communication between the cystically dilated main pancreatic ducts, as well as, intraductal papillary tumor and mucous plugs. MRCP provides a non-invasive method for tumor imaging. MRCP can be preformed using half-Fourier single shot fast spin echo technique (HASTE) with a high sensitivity to detect main pancreatic duct and its branch dilatations.

References:

1. Semelka RC. Abdominal-Pelvic MRI. New York: Wiley-Liss Inc, c2002. pp. 444-445.
2. Lim JH, Lee G, and Oh YL. Radiologic Spectrum of Intraductal Papillary Mucinous Tumor of the Pancreas. Radiographics. 2001; 21: 323-340.
3. Chan W, Wong T, and Tzeng B. Intraductal Papillary Mucinous Tumors of the Pancreas: A Case Report. Chinese Journal of Radiology. 2002; 27: 311-314.