Endocrine cells in islet are considered as the main origin of pancreatic neuroendocrine tumors (PNETs), which serve as a category of relatively rare pancreatic tumors and comprises <5% of all pancreatic tumors. PNETs are featured by remarkable disease heterogeneity leading to difficulty in correct diagnosis and inconsistent clinical outcomes.[1,2] The distant metastases of PNETs are mainly located in liver,[3,4] presenting as solid lesions. In this case, we report a rare case that presents cystic lesions in liver of PNETs. And it possibly misleads our diagnosis of the disease merely depending on CT and MRI imaging, and reminders surgeons the importance of pathology.
A 48-year-old female patient presented with recurrent back pain and abdominal distention for 10 years. This patient has a 5 years history of type 2 diabetes mellitus, and the blood glucose was controlled between 6 to 7 mM by metformin administration. She had no history of hepatitis B virus infection, acute pancreatitis, liver cirrhosis, paroxysmal disturbance of consciousness, or any other symptoms. Physical examination revealed no abnormal signs. The abdominal CT scan detected both pancreatic and hepatic lesions. The pancreatic lesion was presented as a hypodense solid mass located at the pancreatic body and tail with splenic artery invasion, which was not enhanced on both arterial and portal venous phase (Fig. 1 A). The liver lesion was a low-density heterogenous cystic-solid mass in non-contrast phase, but the solid component was significantly enhanced during the arterial phase (Fig. 1 B). As exhibited in the MRI images, the pancreatic lesion showed hypointense signal in T1-weighted imaging, heterogenous signal in T2-weighted imaging and hyperintense signal in diffusion-weighted imaging, and not enhancing in arterial phase (Fig. 1 C). Though the hepatic lesion was a cystic-solid mass dominated by the cystic components. The tumor showed heterogenous hypointense signal in T1-weighted imaging and heterogenous hyperintense signal in T2-weighted and diffusion-weighted imaging. The solid component exhibited hyperintensity in arterial, portal venous and as well as delayed phase (Fig. 1 D). Laboratory tests including routine blood test, liver function, renal function, blood glucose and tumor markers (CEA, AFP, CA125 and CA19-9) were all within the reference range. The ethical approval and written consent were waived by the institutional review board of our hospital owing to the retrospective nature of the study and routine treatments performed on this patient in clinical practice. The informed consent was obtained from the patient.
The patient underwent laparoscopic distal pancreatectomy with splenectomy and partial hepatectomy synchronously. The macroscopy of this pancreatic tumor mimicked that of pancreatic carcinoma, which was firm with irregular margin and retroperitoneal infiltration. The hepatic lesion was a cystic-solid mass with an intact capsule, and incompletely focal necrosis could be observed within the solid portion. The cystic component was filled with blood clot and necrotic debris (Fig. 1 E). Meanwhile, CgA and Syn are expressed in both primary and metastatic lesions as demonstrated by immunohistochemical staining (Fig. 1 F and G). The pancreatic lesion was pathologically validated as neuroendocrine tumor (G2) with Ki-67 index about 10%, while the hepatic lesion was verified as a cystic metastatic lesion with Ki-67 index about 20% (Fig. 1 H and I).
Though liver metastasis is common in gastrointestinal cancers, metastases that exhibit a completely or partially cystic appearance is rare. Cystic liver metastases are more frequently seen in mucinous adenocarcinomas including colorectal cancer or ovarian carcinoma, and PNETs are predominantly present as solid lesions. For these solid primary neoplasms, cystic transformation of liver metastases is usually caused by ischemic necrosis. Cystic liver metastases originated from solid PNETs was rarely reported previously.
PNETs is group of highly heterogenous neoplasms,[9,10] significant differences in biological behavior and imaging characteristics could be observed between the primary and metastatic lesions or even between different metastases. As to this patient, the pancreatic lesion was solid, firm and hypovascular, which was extremely similar to pancreatic ductal adenocarcinoma (PDAC). However, the hepatic lesion was cystic, soft and hypervascular, it became challenging to reveal the intrinsic relationship between these 2 lesions preoperatively. Based on the distinct differences of these 2 lesions, synchronous PDAC and primary hepatic cancer seemed to be a more reasonable diagnosis. However, that was finally negated by postoperative pathology.
This case suggests that the liver metastases of solid pancreatic tumor could be cystic. So when a solid pancreas mass coexists with cystic liver lesion, imaging alone is insufficient to identify the intrinsic relationship between the two lesions. Some special cases can mislead the diagnosis of the disease. Therefore, endoscopic ultrasonography guided fine needle aspiration (EUS-FNA) and liver biopsy are recommended to confirm the diagnosis and help to select optimal treatment.
HH participated in the draft of the manuscript, SH and JY collected and analyzed data, HZ designed the study and participated in the draft and revision of the manuscript. All authors approved the final version of the manuscript.
This work was supported by National Natural Science Foundation of China (Nos. 81600617, 81702365, 81972274).
Conflicts of interest
The authors disclose no conflicts of interest.
The ethical approval and written consent were waived by the institutional review board of our hospital owing to the retrospective nature of the study and routine treatments performed on this patient in clinical practice.
Declaration of patient consent
The authors certify that they have obtained the appropriate consent from the patient. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published and due efforts will be made to conceal her identity.
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