Comparison between solid pseudopapillary neoplasms of the pancreas and pancreatic ductal adenocarcinoma with cystic changes using computed tomography

Abstract

Background: Solid pseudopapillary neoplasms of the pancreas (SPN) share similar imaging findings with pancreatic ductal adenocarcinoma with cystic changes (PDAC with cystic changes), which may result in unnecessary surgery.

Aim: To investigate the value of computed tomography (CT) in differentiation of SPN from PDAC with cystic changes.

Methods: This study retrospectively analyzed the clinical and imaging findings of 32 patients diagnosed with SPN and 14 patients diagnosed with PDAC exhibiting cystic changes, confirmed through pathological diagnosis. Quantitative and qualitative analysis was performed, including assessment of age, sex, tumor size, shape, margin, density, enhancement pattern, CT values of tumors, CT contrast enhancement ratios, "floating cloud sign," calcification, main pancreatic duct dilatation, pancreatic atrophy, and peripancreatic invasion or distal metastasis. Multivariate logistic regression analysis was used to identify relevant features to differentiate between SPN and PDAC with cystic changes, and receiver operating characteristic curves were obtained to evaluate the diagnostic performance of each variable and their combination.

Results: When compared to PDAC with cystic changes, SPN had a lower age (32 years vs 64 years, P < 0.05) and a slightly larger size (5.41 cm vs 3.90 cm, P < 0.05). SPN had a higher frequency of "floating cloud sign" and peripancreatic invasion or distal metastasis than PDAC with cystic changes (both P < 0.05). No significant difference was found with respect to sex, tumor location, shape, margin, density, main pancreatic duct dilatation, calcification, pancreatic atrophy, enhancement pattern, CT values of tumors, or CT contrast enhancement ratios between the two groups (all P > 0.05). The area under the receiver operating characteristic curve of the combination was 0.833 (95% confidence interval: 0.708-0.957) with 78.6% sensitivity, 81.3% specificity, and 80.4% accuracy in differentiation of SPN from PDAC with cystic changes.

Conclusion: A larger tumor size, "floating cloud sign," and peripancreatic invasion or distal metastasis are useful CT imaging features that are more common in SPN and may help discriminate SPN from PDAC with cystic changes.

Keywords: Computed tomography; Differential diagnosis; Pancreas; Pancreatic ductal adenocarcinoma; Solid pseudopapillary neoplasm.

Figure 1

Flowchart of patients throughout the study. CE-CT: Contrast-enhanced computed tomography; CT: Computed tomography; PDAC: Pancreatic ductal adenocarcinoma; SPN: Solid pseudopapillary neoplasms.

Figure 2

Computed tomography images of two cases with solid pseudopapillary neoplasms of the pancreas and pancreatic ductal adenocarcinoma with cystic changes. A: Plain phase computed tomography images showed a hypodensity tumor with a well-defined margin, and calcifications (arrow) were observed within the tumor; B-D: The tumor showed a heterogeneous enhancement pattern in the arterial, portal venous, and delayed phases. Notably, the solid components within the tumor showed enhanced patchy-like structures, which were defined as “floating cloud sign” (arrowhead); E: Plain phase computed tomography images showed a hypodensity tumor with an ill-defined margin (arrow); F: The tumor showed a heterogeneous enhancement pattern with blood vessels wrapped by the tumor in the arterial phase; G and H: The solid components within the tumor showed a slight persistent enhancement pattern. SPN: Solid pseudopapillary neoplasms of the pancreas; PDAC: Pancreatic ductal adenocarcinoma.

Figure 3

Computed tomography images of two cases with solid pseudopapillary neoplasms of the pancreas and pancreatic ductal adenocarcinoma with cystic changes. A: Plain phase computed tomography images showed a hypodensity tumor with an ill-defined margin; B: The tumor showed a heterogeneous enhancement pattern in the arterial phase; C and D: Portal venous and delayed phases showed slight upstream pancreatic duct dilatation; E: Plain phase computed tomography images showed a hypodensity tumor with a well-defined margin (arrow); F-H: The tumor showed a heterogeneous enhancement pattern in the arterial, portal venous, and delayed phases with blood vessels wrapped by the tumor. The solid components within the tumor showed enhanced patchy-like structures with a slight persistent enhancement pattern, which were defined as “floating cloud sign” (arrowhead) (G and H). SPN: Solid pseudopapillary neoplasms of the pancreas; PDAC: Pancreatic ductal adenocarcinoma.

Figure 4

Diagnostic performance of the computed tomography characteristics and their combination (named as “model”) in differentiating pancreatic ductal adenocarcinoma with cystic changes from solid pseudopapillary neoplasms of the pancreas.