Gastrointestinal: Primary pancreatic epithelioid angiomyolipoma

A 50-year-old woman presented to our hospital for the first time with a physical examination of a space-occupying lesion in the head of pancreas and dilation of the common bile duct and pancreatic duct by B-scan ultrasonography. There was no abdominal pain. She had no significant medical or family history. Physical examination was unremarkable, with no abdominal tenderness or mass. Routine blood, liver function test, bilirubin, electrolytes, blood sugar level, Ca 19.9, alpha-fetoprotein, IgG4 level were normal. The CT scan showed that the lesion was located in the head of the pancreas, round, with unclear border and about 18 mm in diameter. The tumor showed moderate heterogeneous enhancement in the arterial phase and decreased enhancement in the venous and delayed phases. The blood vessels and tissues surrounding the tumor had homogeneous enhancement, and no obvious abnormal density was found (Fig. 1). MRCP examination revealed that the common bile duct and pancreatic duct were approximately 14 and 4 mm in diameter, respectively. There was a nodular long T2 signal at the confluence of the common bile duct and pancreatic duct, with a clear border and a diameter of about 16 mm. The three-dimensional reconstructed images from thin-section CT analysis also confirmed these results. EUS also showed hypoechoic lesions in the head of the pancreas. However, no suitable puncture site was found due to the occlusion by dilated ducts and vessels around the lesion. Contrast EUS illustrated a marked enhancement in the arterial phase and regression in the venous phase, suggesting a possible diagnosis of pancreatic neuroendocrine tumor. The patient underwent pancreaticoduodenectomy, and the dissection of the specimen found that the tumor was located at the confluence of the bile duct and pancreatic duct, with a diameter of about 18 mm, a clear boundary, and a purple-black color. The final diagnosis was pancreatic epithelioid angiomyolipoma, based on the strong positive for HMB45 and cyclin D1 staining, weakly positive for melan-A staining, negative for S100 staining, repeated physical examination, and no medical or family history of melanoma. The proliferation index (Ki67) was calculated as 10%. The patient recovered well postoperatively without complications. No postoperative radiotherapy, chemotherapy, or other adjuvant therapy was performed, and there was no evidence of tumor recurrence or metastasis during the 14-month follow-up.