Clinical features and CT/MRI findings of pancreatic acinar cell carcinoma

Abstract

To retrospectively review the clinical features and computed tomography (CT) and magnetic resonance imaging (MRI) findings of PAAC so as to improve the accuracy of imaging diagnosis. Seventeen patients with pathologically proven PAAC were enrolled. Their clinical and imaging findings were retrospectively reviewed. The median age of the patients was 56 years (range, 7-74 years). The tumors were located in any part of the pancreas or exophyitc growth, with a median maximal diameter of 68 mm. Thirteen masses presented with ovoid shape. Nine masses had less clear boundaries. Eleven masses showed a variable degree of intratumoral hypodense or necrosis before contrast administration on CT images. Five masses showed hypointense on unenhanced T1 weighted images and hyperintense on T2 weighted images. After contrast administration, the most common enhancement pattern was slight enhancement on arterial phase and persistent enhancement on portal vein phase. Infiltration of tumor into duct and vessels was not common. Five and 2 patients developed hepatic metastasis and local lymphadenopathy, respectively. By the end of the last follow-up, 11 patients survived free of disease. PAAC should be included in the differential diagnosis when a bulky, ovoid, heterogeneous mass, with clear or less clear margins, in the pancreas or peripancreas, with slight and persistent enhancement after contrast administration on CT or MRI images is seen, particularly in elder men.

Keywords: Pancreatic acinar cell carcinoma; clinical feature; computed tomography; magnetic resonance imaging.

Figure 1

A 54-year-old male with ACC in the body and tail of the pancreas. A. Unenhanced axial CT image showed an ovoid and well-circumscribed mass in the body and tail of the pancreas, with roughly uniform density. B. The mass revealed mild enhancement in the arterial phase when compared to the normal pancreas. C. The mass showed persistent enhancement in the portal vein phase.

Figure 2

A 15-year-old male with ACC in the body and tail of the pancreas. A. Unenhanced axial CT image showed an ill-circumscribed mass in the body and tail of the pancreas with irregular shape. Strip-shaped calcification was found in it. B. The mass revealed intense enhancement in the arterial phase compared with the pancreatic tissue. C. The contrast agent in the mass washed out in the portal vein phase.

Figure 3

A 53-year-old male with an exophytic ACC. A. Coronal T1 weighed MR image demonstrated an exophytic mass in the left peritoneal cavity, with ovoid shape and clear margin. The mass had a hypointense signal. B. The mass had a heterogeneous, hyperintense signal on the fat-suppressed T2 weighted MR image. C. The mass presented mild enhancement on the fat-suppressed and enhanced T1 weighted MR image in the arterial phase. D. The mass showed persistent enhancement in the portal vein phase.

Figure 4

A 59-year-old male with ACC in the head and neck of the pancreas. A. Unenhanced axial CT image showed a mass in the head and neck of the pancreas with ovoid shape and unclear margin. The mass demonstrated a relatively large area of hypodense (white arrow) and patchy hemorrhage (black arrow). B. The mass showed intense enhancement in the arterial phase compared with the pancreatic tissue. C. The contrast agent in the mass washed out in the portal vein phase. A nodule was found in the right and posterior hepatic lobe, which was pathologically confirmed a metastatic lesion of ACC (black arrow). D. The different axial section of the same mass showed the thrombus in the main portal vein (black arrow).

Figure 5

Dilation of bile duct and pancreatic duct of patients with ACC. A. A 13-year-old female with ACC. Enhanced coronal CT image showed that the mass located in the head of the pancreas (M) which infiltrated the common bile duct, resulting in dilation of intrahepatic bile duct and common bile duct. B. A 65-year-old female with ACC. Enhanced axial CT image showed that the mass in the pancreatic neck infiltrated the main pancreatic duct, leading to dilation of the distal pancreatic duct (white arrow).

Figure 6

Metastasis of the liver and lymph nodes in the patients with ACC. The same patients as that of Figure 5A. The patients developed hepatic and lymphatic metastasis 1 year after operation. Enhanced axial CT image showed the hepatic nodules (black arrows) and the enlarged lymph nodes in the hepatic hilar region and the periphery of vena cava (white arrows).

Figure 7

Acinar formation of the neoplastic cells of PACC. The neoplastic cells revealed acinar pattern (white arrow, original magnification ×200).