Imaging features of intraductal tubulopapillary neoplasm of the pancreas and its differentiation from conventional pancreatic ductal adenocarcinoma

Abstract

Intraductal tubulopapillary neoplasms (ITPN) are rare pancreatic tumors (< 1% of exocrine neoplasms) and are considered to have better prognosis than classical pancreatic ductal adenocarcinoma (PDAC). The present study aimed to evaluate imaging features of ITPN in computed tomography (CT) and magnetic resonance (MR) imaging. We performed monocentric retrospective analysis of 14 patients with histopathologically verified ITPN, operated in 2003-2018. Images were available for 12 patients and were analysed independently by two radiologists, blinded to reports. Imaging features were compared to a matched control group consisting of 43 patients with PDAC, matched for sex and age. Histopathologic analysis showed invasive carcinoma component in all ITPN patients. CT-attenuation values of ITPN were higher in arterial and venous phases (62.3 ± 14.6 HU and 68 ± 15.6 HU) than in unenhanced phase (39.2 ± 7.9 HU), compatible with solid lesion enhancement. Compared to PDAC, ITPN lesions had significantly higher HU-values in both arterial and venous phases (arterial and venous phases, p < 0.001). ITPN were significantly larger than PDAC (4.1 ± 2.0 cm versus 2.6 ± 0.84 cm, p = 0.021). ITPN lesions were more often well-circumscribed (p < 0.002). Employing a multiple logistic regression analysis with forward stepwise method, higher HU density in the arterial phase (p = 0.012) and well-circumscribed lesion margins (p = 0.047) were found to be significant predictors of ITPN versus PDAC. Our study identified key imaging features for differentiation of ITPN and PDAC. Isodensity or moderate hypodensity and well-circumscribed margins favor the diagnosis of ITPN over PDAC. Being familiar with CT-features of these rare pancreatic tumors is essential for radiologists to accelerate the diagnosis and narrow the differentials.

Figure 1

Box plots demonstrating attenuation differences in the group with ITPN and PDAC in the arterial and venous phases.

Figure 2

Comparison of CT features of ITPN with associated invasive carcinoma and PDAC. (A) Axial CT scan in the portal venous phase showing ITPN lesion in the pancreatic head (arrow) with well-circumscribed margins and isodense HU values. Note the preserved morphology and boundaries of the superior mesenteric vessels. (B) Axial CT scan of a different patient in the portal venous phase showing PDAC in the same location (arrow) showing unsharp margins, hypodensity und classical tear-drop sign of superior mesenteric vein (dotted arrow), suggesting its infiltration.

Figure 3

CT and MRI features of ITPN with associated invasive carcinoma. (A,B) Axial CT scans in the arterial phase (A) and portal venous phase (B) demonstrating ITPN lesion in the pancreatic tail (arrows) with well-circumscribed margins and moderate hypointense HU values. (C) Axial T2 weighted image of the same patient, tumor (arrow) doesn’t have classical cystic morphology on T2 but is slightly T2 hyperintense compared to pancreatic parenchyma. (D) Axial T1 weighted image with fat suppression after CM administration, portal venous phase. Tumor (arrow) shows low inhomogeneous contrast enhancement without invasion of adjacent structures. (E,F) Tumor (arrows) shows hyperintensity on axial DWI with b-value 800 s/mm² (E) and hypointensity on ADC map (F), which corresponds the restricted diffusion.

Figure 4

ITPN mimicking the morphology of mucinous cystic neoplasm. (A,B) Axial CT scans in the arterial phase (A) and portal venous phase (B) demonstration a huge oligocystic mass (arrow) in the pancreatic head with an enhancing solid nodular component (dotted arrow).

Figure 5

Cystic pancreatic lesions with development of solid ITPN in the pancreatic body. (A,B) Initial MRI study with cystic pancreatic lesions. (A) Axial T2 weighted image shows small cystic lesions (arrows) in the pancreatic tail without dilatation of the main pancreatic duct, suggesting small branch duct IPMNs. (B) Axial T1 weighted image after contrast medium administration in the portal venous phase. Tiny cystic lesion without contrast enhancement (arrow). No evidence of the tumor in the pancreatic body. (C–F) Follow-up of the same patient in 7 years. (C) Axial T2 weighted image, known cystic lesions in the pancreatic tail significantly increased in size (arrow). (D) Axial T1 weighted image after contrast medium administration in the portal venous phase. New lesion in the pancreatic body showing solid pattern of contrast enhancement being almost isointense to pancreatic parenchyma. (E) Axial T2 weighted image, elongated solid lesion within the pancreatic body (dotted arrows), which was histologically confirmed as ITPN after resection. (F) DWI with b-value 800 s/mm² with restricted diffusion within the lesion.

Figure 6

CT and MRI features of ITPN with intraductal solid tumor growth. (A) Axial CT scan in the portal venous phase shows an ITPN lesion in the pancreatic head (arrow) with well-circumscribed margins and slightly hypodense HU-values, compared to normal pancreatic parenchyma. (B) Axial T2 weighted image of the same patient. The lesion had T2 hypointense signal (arrow), suggesting a solid morphology. (C,D) Coronal T2 weighted image (C) and axial T2 weighted image (D) show dilated main pancreatic duct with intraductal solid tumor growth (dotted arrows). (E,F) T1 weighted images with fat suppression after contrast administration in the arterial (E) and venous (F) phase. In both phases tumor is hypointense to pancreatic parenchyma without significant contrast enhancement.