A Case of Pancreatic Desmoid Tumor Treated by Laparoscopic Distal Pancreatectomy

The patient was a 72-year-old man who had undergone lower anterior resection for a rectal neuroendocrine neoplasm four years ago. CT showed a mass lesion in the tail of the pancreas, contrast-enhanced CT indicated an enhanced 16-mm mass, and diffusion-weighted MRI showed a hyperintense mass. On PET-CT, the appearance of a hyperintense mass suggested a malignant tumor. Laparoscopic distal pancreatectomy was performed under a diagnosis of a metastatic pancreatic tumor from a rectal neuroendocrine neoplasm. The tumor was exposed on the ventral side of the tail of the pancreas and was found to have partially invaded the surrounding adipose tissue. A histological examination revealed proliferation of spindle-shaped tumor cells, and an immunohistological examination showed vimentin(+) and β-catenin(+) findings. The pathological diagnosis was a desmoid tumor of the pancreas. Desmoid tumor is often associated with familial adenomatous polyposis, but the etiology is unknown. This tumor is a borderline tumor with no potential for metastasis; however, it exhibits local invasiveness that indicates clinical malignancy. Desmoid tumor of the pancreas is extremely rare and laparoscopic surgery is difficult to perform because of the locally invasive behavior of the tumor. The prognosis of pancreatic desmoid tumor resected laparoscopically is unclear, and careful attention will be paid to the long-term oncologic outcome in our case.