Pancreatic tumors: emphasis on CT findings and pathologic classification

Abstract

Pancreatic tumors can be classified by their morphologic features on CT. The subtypes include solid tumors, mixed cystic and solid lesions, unilocular cysts, multilocular cystic lesions, and microcystic lesions. Endoscopic US and MRI can provide detailed information for classifying pancreatic lesions. Each subtype has different kinds of tumors and malignant potential, thus the classification can be useful for a better differential diagnosis and treatment planning. For this purpose, we suggest an appropriate modified classification system by using the imaging features of pancreatic tumors with an emphasis on CT findings and illustrate various findings of typical and atypical manifestations.

Keywords: Computed tomography; Endoscopic ultrasound (EUS); Magnetic resonance imaging (MRI); Pancreatic tumors.

Fig. 1

Morphologic subtypes of pancreatic lesions. Because each pancreatic neoplasm has different malignant potential, it is clinically valuable to determine characteristic imaging findings that can enable differentiation. We classified pancreatic tumors into solid tumors (A malignant or potentially malignant), mixed cystic and solid lesions (B malignant or potentially malignant), unilocular cysts (C benign or potentially malignant), multilocular cystic lesions (D benign or potentially malignant), and microcystic lesions (E benign). Multilocular cystic lesions are divided into three categories including lobulated (benign), pleomorphic (from benign to malignant), and smooth in shape with septation (potentially malignant). These figures are made by referring to previously suggested classification schema (5).

Fig. 2

58-year-old woman with metastatic leiomyosarcoma manifesting as solid lesion. A. Contrast-enhanced CT image during venous phase shows well-marginated, low attenuating solid tumor in pancreas (white arrow). B. Endoscopic US image depicts heterogeneously hypoechoic solid tumor (white arrow). Woman had multiple painless metastatic tumors in her stomach, chest, thigh and pancreas, which were too numerous to excise. Consequently, surgery was ruled out, and only chemotherapy was performed. C. Woman began to feel sick and mass increased in size at 1-year follow-up CT. Note metastatic nodule in subcutaneous layer (white arrow). D. Tumor was finally excised and appeared as whitish solid tumor in gross specimen and was confirmed as metastatic leiomyosarcoma (white arrow).

Fig. 3

40-year-old man with cystic change of islet cell tumor manifesting as mixed cystic and solid lesion. A. Contrast enhanced CT image during arterial phase shows two unilocular cystic lesions with small solid components in tail of pancreas (white arrow). B. T2-weighted image shows cystic character of lesions (white arrow). C. Surgical specimen shows two predominantly cystic lesions with solid portion and small mural nodules. Microscopic examination revealed cystic change of islet cell tumors (black arrows).

Fig. 4

57-year-old woman with mucinous cystic neoplasm manifesting as unilocular cyst. A. Transverse contrast enhanced CT image during arterial phase shows unilocular cyst (white arrow) in body of pancreas. B. Endoscopic US image depicts cyst without solid portion or septation. C. Gross specimen reveals unilocular cystic lesions without septation or solid mural nodule (white arrow). Communication with pancreatic duct was not found. Tumor was confirmed as mucinous cystadenoma.

Fig. 5

47-year-old woman with lymphoepithelial cyst manifesting as unilocular cyst. A. Transverse contrast enhanced CT image during arterial phase shows unilocular cystic lesion in tail of pancreas (white arrow). B. Endoscopic US image shows homogeneous echoic cystic lesion. C. Surgical specimen shows round tumor with surrounding fibrous capsule (white arrow).

Fig. 6

27-year-old woman with mucinous cystic neoplasm manifesting as multilocular cystic lesion (smooth shape with septation). A. Contrast enhanced CT image during venous phase obtained after intravenous injection of contrast material reveals smooth-shaped cystic lesion in tail of pancreas. B. Axial T2-weighted MR image reveals multiple internal septa in cystic lesion. C. Endoscopic US image also depicts multilocular cystic lesion with smooth shape and multiple inner septa, which was consistent with mucinous cystic neoplasm.

Fig. 7

37-year-old woman with serous cystadenoma manifesting as multilocular cystic lesion (lobulated). A. Contrast-enhanced CT image during venous phase shows multilocular cyst in body of pancreas. Lobulated shape of tumor corresponds to polycystic serous cystadenoma rather than mucinous cystadenoma. B. Endoscopic US depicts tumor composed of multiple cysts. Endoscopic US-guided aspiration showed no malignant cell. C. Ill-defined multilocular cystic tumor with inner smooth and trabeculated surface is seen in gross specimen (white arrows) and confirmed as serous cystadenoma composed of variable sized cysts lined by simple cuboidal cells.

Fig. 8

43-year-old man with branch duct type intraductal papillary mucinous neoplasm manifesting as multilocular cystic lesion (pleomorphic cystic). A. Contrast enhanced CT image during venous phase shows multilocular pleomorphic cystic lesion in head of pancreas. B. Note dilated downstream pancreatic duct (black arrow). C. Gross specimen showing ill-defined multilocular cystic tumor in head of pancreas (black arrow) which contained mucinous material. Tumor connects with irregularly dilated branches of pancreatic duct, and is confirmed as branch duct type intraductal papillary mucinous neoplasm.

Fig. 9

52-year-old man with invasive intraductal papillary mucinous neoplasm. A. Contrast-enhanced CT image during venous phase shows dilatation of main pancreatic duct with adjacent solid mass in head of pancreas (white arrows). B. Endoscopic US image shows cystic lesion with inner solid portion (white arrow). C. Surgical specimen shows tumor involvement of dilated main pancreatic duct (white arrow). Microscopic examination revealing invasive intraductal papillary mucinous neoplasm.

Fig. 10

66-year-old man with microcystic serous cystadenoma manifesting as microcystic lesion. A. Contrast-enhanced transverse CT during arterial phase shows hypervascular mass (white arrow) in tail of pancreas. It appears as solid lesion on CT, owing to innumerable cysts and fine septa. B. Note cystic portion in periphery of tumor (white arrow). C. Axial T2-weighted image reveals microcystic mass. D. Gross specimen shows multilocular, well-defined bulging mass containing multiple tiny cystic spaces and sanguineous clear fluid (white arrow), which are confirmed as microcystic serous cystadenoma.

Fig. 11

37-year-old woman with mucinous cystic neoplasm: pitfall in differentiating multilocular cystic lesions. A. Contrast-enhanced CT image during venous phase shows multilocular lobulated cyst with internal septation and calcification in tail of pancreas. B. Coronal T2-weighted image reveals multilocular cystic mass. C. T1-weighted gradient-echo image shows multiple locules with different signal intensity (black and white arrows). D. Gross specimen shows multilocular cystic tumor with inner smooth and glistening surface (white arrow) which was confirmed as mucinous cystadenoma at microscopy.

Fig. 12

59-year-old-woman with branch duct type intraductal papillary mucinous neoplasm manifesting as mixed cystic and solid lesion. A. Contrast-enhanced CT image during venous phase shows cystic mass and internal solid portion in head of pancreas (white arrow). B. Two-dimensional thick slab MR cholangiopancreatography image shows cystic mass in head of pancreas. Communication between cystic mass and pancreatic duct is not clear. C. Source image of 3D-MR cholangiopancreatography shows narrow tumor neck suggesting communication between tumor and main pancreatic duct more clearly than 2D-MR cholangiopancreatography (white arrow). D. Gross specimen shows whitish polypoid friable mass containing translucent mucoid materials. Tumor communicates with main pancreatic duct (white arrow) and was confirmed as branch duct type intraductal papillary mucinous neoplasm.