|ECR 2013 / C-1474|
|Imaging and pathological findings of solid pseudopapillary tumor of the pancreas: a report of 53 cases|
- Location: 23 in head, 15 in tail, 14 in body and tail with an obscure boundary, and 1 in neck.
- Morphology and diameter: 90.9% (46 of 53) were round or ellipse and 9.1% (7 of 53) appeared to be nodular or lobular.
- The average maximum diameter of tumors is 5.8cm(range, 1-13)±2.9 (standard deviation) .
- Internal components: 83% (44 of 53) tumors were cystic-solid masses constituted with varied solid portion and 75.5% (40 of 53) had more than 50% solid portion. 15.1% (8 of 53) were purely solid and 1.9% (1 of 53) was purely cystic.
- Capsule: 77.4%(41 of 53) SPTs were well defined with a capsule and 22.6% (12 of 53) were absent of capsule.
- Calcification and hemorrhage: Calcification was noted in 28.3% (15 of 53) SPTs. Hemorrhage was found in 24.5% (13 of 53) cases with an average maximum diameter of 6.7cm (range 3-12).
Comparison between different size groups
53 SPTs were divided into three groups according to size. Clinical features and imaging findings are shown in Table 1.
- The mean age of patients with small SPTs was significantly different from that of the patients in large group (P<.05; Mann-Whitney test).
- The frequency of complete solid tumors was higher among the small group (65%, 5 of 9) (P=.001).
- There was a significant difference in capsule presentation within the three groups (P<.05).
- Significant difference of hemorrhage observed on imaging existed between middle SPTs and large SPTs (P<.05).
- The enhancement pattern during pancreatic phase of three groups was significantly different (P<.05 or P<.001).
Comparison between different age and gender groups
Comparison of image features between different age and gender groups were showed in Table 2.
- The mean size of the younger patients was larger than that of the older group (P=.004 in diameter; Mann-Whitney test).
- There was no significant difference between the female and male patients in imaging features listed in Table 2.
Comparison between benign and malignant groups
Comparison between benign SPTs and SPCs were showed in Table 3(Omitted).
- Significant difference was found only in metastasis between the two groups.
- Computed tomography scans showed a cystic-solid, solid or cystic mass with heterogeneous attenuation in 44 patients. The arterial phase showed a slight or moderate intensity of solid portion. Enhancement was slightly increased in the pancreatic phase. Progressive delayed reinforcement was noted in the portal venous phase.(Fig1).
- In the pancreatic phase, heterogeneous or homogeneous enhancement was noted in 40 cases and peripheral enhancement was noted in one case. Minimal enhancement was observed in 3 small SPTs during the pancreatic phase, after which they gradually enhanced during the portal venous phase and are isoattenuating to the surrounding pancreatic tissue (Fig2).Calcification, dilation of pancreatic duct and infiltration to adjacent pancreatic parenchyma could be observed in small SPT.
- Hemorrhage was observed in 9 cases, showing distinctive high signal in T1WI and high, low or mixed signal in T2WI without enhancement and stratified hemorrhage was noted (Fig 3).
- The dynamic enhancement pattern on T1-weighted images was classified as follows: persistent homogeneous enhancement (0 of 18), early heterogeneous and progressive enhancement (14 of 18) (Fig 3,4), early heterogeneous and no progressive enhancement (2 of 18). Peripheral enhancement (1 of 18) or minimal enhancement (1 of 18) was observed in small SPT.
- 45 cases were benign SPTs and 8 were SPCs, with an average maximum diameter of 4.8 cm (range1-6.4).
- 7 SPCs had more than 50% solid portion and 2 had lymph node metastasis.
- SPTs with specific vessels and nerves invasion, invasion to adjacent pancreatic parenchyma or organs, lymph nodes involvement and metastasis were defined as SPCs (Fig 4).
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