Intraductal Papillary Mucinous Tumor of the Pancreas: A Pictorial Essay

Abstract

Intraductal papillary mucinous tumor (IPMT) of the pancreas was identified and classified only recently. IPMT has a primarily intraductal, papillomatous growth pattern, which is associated with excessive mucin secretion and results in progressive ductal dilatation or cyst formation. The tumor occurs in four forms: segmental or diffuse involvement of the main pancreatic duct and macrocystic or microcystic involvement of a branch duct. In the past, many IPMTs may have been misdiagnosed as chronic pancreatitis because of their generally benign behavior. The correct diagnosis, once achieved only with endoscopic retrograde cholangiopancreatography (ERCP), can now be made with noninvasive imaging modalities, particularly computed tomography (CT) and magnetic resonance (MR) imaging. ERCP remains the imaging modality of choice for diagnosis of IPMT. With ERCP, the communication between the cystically dilated ductal segment or branch duct and the main pancreatic duct is easily demonstrated. However, reflux of contrast material due to an excess of mucin or an enlarged papillary orifice hinders filling of the ductal tree. Filling defects due to mucin globs or mural nodules are also important clues to the diagnosis. Bulging of the papilla into the duodenal lumen is virtually pathognomonic of IPMT and is well demonstrated with CT or MR imaging.

Utility of Multidetector Row CT in Diagnosing Branch Duct IPMNs of the Pancreas Compared with MR Cholangiopancreatography and Endoscopic Ultrasonography

“…In addition, the presence of thickened irregular walls/septa on MDCT also correlated well with malignancy. Procacci et al [17] reported that in malignant lesions, the wall and septa appear irregular and thick, indicating intramural nodules, whereas both the wall and septa are regular and thin in benign lesions. Carbognin et al [18] reported that the presence of a thick wall by CT and MR imaging is strongly suggestive of malignancy.…”

Case 136: Intraductal Papillary Mucinous Tumor (Main Duct Type) of the Pancreas

“…Approximately 75% of IPMTs originate from the main pancreatic duct within the head of the pancreas (3). Imaging of IPMTs is important not only to identify the tumor but also to determine the appropriate treatment strategy in relation to the site and size of the lesion (2). Although the presence of a dominant mass of considerable size (as in the present case) is a rare occurrence, it should not preclude the diagnosis of IPMT.…”

“…IPMTs occur with equal frequency in male and female subjects, and the peak time of occurrence is the 6th decade of life, regardless of sex (2). Approximately 75% of IPMTs originate from the main pancreatic duct within the head of the pancreas (3).…”

“…Intraductal filling defects can be seen in the main duct. These defects represent mucin globules, papillary projections of the tumor that are hyperechoic on US images, or both (2,5). At CT, unenhanced mucin deposits can be distinguished from contrastenhanced papillary proliferations (5).…”

Contrast-enhanced ultrasound of the pancreas

“…the identification of vascularized inclusions (Figure 4), and for the differential diagnosis between MCA and a pseudocyst [17,46] . IPMNs are cystic tumors of the pancreas recently reported with increasing frequency [6,38,41,47,48] . They are macroscopically characterized by having an intraductal origin and growth [49] , with the production of dense mucin that fills the main pancreatic duct (the ductectatic mucin-hypersecreting variant) or with endoluminal papillary proliferation (the papillary-villous variant).…”