Pancreatic lipoma diagnosed using EUS-FNA. A case report.

CONTEXT Pancreatic mesenchymal tumors are rare, accounting for only 1-2% of pancreatic tumors. A pancreatic lipoma is an especially rare condition. This is only the second report of a pancreatic lipoma diagnosed before surgery using endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNA). CASE REPORT A 75-year-old woman with a round low-density lesion which had been detected by CT was referred to our hospital. EUS revealed an oval 49x32 mm homogeneous and almost isoechoic mass (as compared to normal pancreatic parenchyma) in the pancreatic head. Its outer margin was not clearly differentiated from the parenchyma. Although a benign pancreatic lipomatous lesion was deemed most probable from information obtained using CT/MRI, a mass with malignancy such as a liposarcoma could not be ruled out as a differential diagnosis. Therefore, EUS-FNA was performed for a definitive diagnosis. Two passes were performed with on-site pathology. The results obtained from the sample analysis indicated a pancreatic lipoma consisting of mature fat cells with no atypia. CONCLUSION Although imaging modalities are useful for the diagnosis of pancreatic lipomatous lesions, it is sometimes difficult to diagnose lipomatous malignancies mimicking benign lipoma. This case demonstrates the usefulness of EUS-FNA for the differential diagnosis of pancreatic lipomatous lesions.