Although there are many potential causes of acute abdomen, spontaneous abdominal hemorrhage (defined as non-traumatic and non-iatrogenic intra-abdominal bleeding) is a particularly rare, life-threatening cause [6]. Visceral sources of spontaneous intra-abdominal bleeding have been reported and include an underlying hypervascular tumor [6], spontaneous rupture of hepatocellular adenoma (adenocarcinoma) [7], renal cell carcinoma [8], renal angiomyolipoma [9], adrenal pheochromocytoma [10], and gastrointestinal stromal cell tumor [11]. However, a pancreatic tumor is an extremely rare source of spontaneous intra-abdominal bleeding. A review of the literature revealed only 10 previous case reports of spontaneous rupture of pancreatic tumors such as mucinous cyst neoplasms [12, 13], pancreatic neuroendocrine cell tumors [14, 15], solid cystic tumors [16, 17], acinar cell carcinoma [18], pancreatoblastoma [19], and metastasis from other cancers [20, 21]. To the best of our knowledge, no previous English-language report has described spontaneous intra-abdominal bleeding due to rupture of UCP. The reported cases of spontaneous rupture of the pancreas are summarized in Additional file 1: Table S1. Seven patients were female, including two pregnant women, and four patients were male. All patients’ chief complaint was acute-onset upper abdominal pain. Several patients’ general condition rapidly deteriorated after admission. Emergency laparotomies were carried out in all 11 patients. In two patients, internal drainage or cyto-reduction/debulking surgery was chosen because of the patient’s general condition or older age, whereas pancreatectomy was successfully performed in the remaining nine patients. One patient who underwent internal drainage died of severe sepsis originating from a urinary tract infection 3 months postoperatively.
UCP is an extremely rare tumor. In the Pancreatic Cancer Registry in Japan, in which 28,655 cases of pancreatic neoplasms were registered from 1981 to 2004, UCP represents only 0.1% of all pancreatic exocrine neoplasms [22]. The median survival duration of these patients with UCP was 3.3 months, and the 1- and 2-year overall survival rate was 14.4% and 0.0%, respectively. A previous study of 60 cases of UCP showed that UCP tended to present in men (63%) and to be located at the pancreatic head (53%) [23]. The serum concentration of carbohydrate antigen 19-9 (CA19-9) was not elevated in our patient. This is consistent with a previous report in which patients with UCP presented with an elevated serum CA19-9 concentration less frequently than did patients with pancreatic ductal adenocarcinoma [24].
CECT is reportedly essential for prompt diagnosis of intra-abdominal bleeding [6]. We also diagnosed intra-abdominal bleeding due to a pancreatic tumor before surgery based on the CECT findings in this case, but UCP was difficult to diagnose before surgery. According to a previous review of UCP, tumor or rim enhancement on CECT was observed in 82% of cases, and a cyst-like structure was found in the lesion in 47% of cases. The preoperative differential diagnoses were a cystic neoplasm (including intraductal papillary neoplasm, mucinous cystic neoplasm, or serous cystic neoplasm), neuroendocrine neoplasm, acinar cell carcinoma, or solid-pseudopapillary neoplasm, which are occasionally accompanied by hemorrhage, necrosis, and subsequent cystic degeneration within the lesion [23].
In the resected specimens of our case, the tumor was rubbery and fleshy and exhibited cyst formation, hemorrhage, extensive necrosis, and gross infiltration into the adipose tissue. These findings are consistent with the above-mentioned report of a large series of UCP and were presumably due to rapid tumor growth, intra-tumoral hemorrhage, necrosis, and subsequent cystic degeneration [23].
Because of the extremely low incidence of UCP, survival data are controversial and the survival benefit of surgery for UCP remains uncertain. No therapeutic strategies for UCP have been established. A previous report of 35 patients with UCP demonstrated that the 1-, 2-, and 5-year overall survival rates were 59.1%, 30.7%, and 12.2%, respectively, which are comparable with those of pancreatic ductal adenocarcinoma [2]. These results suggest that the survival benefit of radical resection of UCP is similar to that of pancreatic ductal adenocarcinoma. The pathological findings in our case revealed UCP with osteoclast-like giant cells, which was initially described in 1968 by Rosai [25] as a variant of undifferentiated carcinoma. UCP with osteoclast-like giant cells is less aggressive and presumably has a better prognosis than invasive ductal adenocarcinoma of the pancreas [24]. Surgical resection is reasonable when it is possible. Although there is such pathological type associated with hemorrhage as choriocarcinoma with early vascular invasion [26], intra-tumoral hemorrhage does not frequently occur to UCP with osteoclast-like giant cells. In our case, intra-abdominal hemorrhage was caused by the rupture of the distension tumor with intra-tumoral hemorrhage due to the invasion of the tumor cells to splenic vein under anticoagulation therapy.
We have herein reported an extremely rare case of spontaneous rupture of an undifferentiated UCP presenting as intra-abdominal bleeding. Obtaining a correct preoperative diagnosis was quite difficult at the first evaluation. As indicated by our case, UCP with osteoclast-like giant cells should be considered as a differential diagnosis of pancreatic tumors.