A case of a malignant serous neoplasm of the pancreas with synchronous vascular invasion and metachronous metastases

Serous neoplasms (SNs) of the pancreas are usually considered benign tumors. However, they rarely manifest malignant behaviors. Here we present a case of malignant SN and review the literature of malignant SN. A 71-year-old woman presented to our hospital with a palpable abdominal mass. Imaging studies revealed a 7 cm mass with a cluster of microcysts having a honeycomb appearance in the head of the pancreas, which invaded the superior mesenteric vein (SMV). After being clinically diagnosed with SN, pancreaticoduodenectomy was performed with resection of limited SMV. Microscopically, the tumor was diagnosed as an SN concomitant with the tumor thrombus in the SMV. Four years after the surgery, two liver tumors and two peritoneal nodules were detected and three of them were surgically resected. All of those lesions had a honeycomb appearance in their cut surfaces and they were microscopically indistinguishable from the originally resected SN. A review of the literature identified 22 cases of malignant metastatic SNs published to date. Even though extremely rare, metachronous metastasis could occur in SNs of the pancreas. Local invasion indicated an increased likelihood of future metastasis. Thus, periodic surveillance should be considered for SNs after resection, especially when they have a local invasion.