Pancreatic abscess caused by Corynebacterium coyleae mimicking malignant neoplasm.

A 50-year-old female was referred to our hospital because of postprandial epigastric pain and pancreatic head mass. On admission, an elastic hard mass with tenderness was palpable in the epigastric region. Laboratory findings showed no abnormalities, except for a slightly elevated C-reactive protein value and iron deficiency anemia. Serum levels of pancreatic enzymes and tumor markers were also within the reference range. Computed tomography (CT) demonstrated a 5-cm heterogenous mass at the head of the pancreas. Angiography showed that gastroduodenal artery was transformed and narrowed by the mass. Smooth stenosis of portal vein was also observed. Fusion CT-positron emission tomography with 2-deoxy-2-[F]fluoro-D-glucose demonstrated a focus of increased uptake in the pancreatic head mass. We suspected the mass of malignancy but, surprisingly, tumor size was gradually decreased without any therapies. Biopsy specimens from the mass of the pancreas showed marked inflammatory cell infiltration and marked interstitial fibrosis without malignant cells. Thereafter, we could isolate Corynebacterium coyleae from the biopsy specimen. We diagnosed the mass as a pancreatic abscess caused by C. coyleae and started with the intravenous antibiotics therapy. Subsequent follow-up CT and ultrasonography showed dramatic improvement in pancreatic mass. We present here a case of pancreatic abscess which was difficult to differentiate from malignant lesion by various imaging studies. Moreover, we could culture and identify C. coyleae which had never been reported to be the source of pancreatic abscess.