A Case of Solid Pseudopapillary Neoplasm Spontaneously Ruptured Into the Duodenum: Case Report

Solid pseudopapillary neoplasm (SPN) of the pancreas is an uncommon pancreatic tumor first described by Frantz¹ in 1959, and was included in the World Health Organization classification of tumors in 1996.^2,3 It represents 1% to 2% of pancreatic neoplasms and 10% to 15% of cystic tumors of the pancreas.⁴ Although SPN is known to have a low malignant potential and most patients with SPNs have a favorable prognosis after radical resection, a considerable number of cases with microscopic invasion to adjacent organs including the portal vein (PV), duodenum, spleen, or kidney were reported.^5,6 However, there have been no reports of ruptured SPN into adjacent organs. Herein, we report a rare case of SPN that spontaneously ruptured into the duodenum and was successfully resected by pancreaticoduodenectomy combined with PV resection.

Case Presentation

The patient has given permission to publish her case. The patient was a 22-year-old female who visited another hospital in November 2012 with a complaint of upper abdominal and back pain. Abdominal computed tomography (CT) showed a well-defined heterogeneous 8-cm mass with calcification in the pancreatic head. Duodenum and PV were distorted by the tumor. Dilatation of the main pancreatic duct was also observed (Figs. 1A and 1B). Magnetic resonance imaging (MRI) revealed a mass that was encapsulated by a fibrous membrane containing a solid part and various intensities of hemorrhage (Figs. 1C and 1D). The patient was referred to our hospital for surgical treatment in December. At that time, her body temperature was 37.6°. Laboratory tests showed an abnormal elevation of C-reactive protein to 16.5 mg/dL. To investigate the inflammation's origin, a re-examination of another abdominal CT was performed at our hospital. The results of CT indicated that her inflammation was due to tumor rupture into the duodenum, because the mass was evidently reduced in size to 5 cm and contained air (Fig. 2). Since she had no history of blunt abdominal trauma, the tumor was considered to have ruptured spontaneously. Endoscopic ultrasound-guided fine-needle aspiration was performed for histologic diagnosis. From the results, she was diagnosed with pathologic solid pseudopapillary neoplasm. She underwent operation in January 2013. On laparotomy, the tumor invaded the superior mesenteric vein and duodenum. Therefore, subtotal stomach preserving pancreaticoduodenectomy with combined resection of PV was performed. First, a wedge resection of PV was performed. However, since the intraoperative pathologic examination revealed the PV wall margin to be positive for SPN cells, an additional segmental resection of PV was done. The procedure took 458 minutes and involved 740 mL of blood loss. The resected specimen showed an 8 × 5.5-cm tumor in the pancreatic head. Before opening the duodenum, contrast radiography of the resected specimen was performed. The contrast medium injected into the tumor leaked out from the 2nd portion of the duodenum (Fig. 3). The gross appearance of the cut surface revealed an encapsulated round tumor composed of a solid area and hemorrhage. The cystic part of the tumor mostly existed close to the duodenum while the solid part existed at the peritoneal side (Fig. 4A). Histologically, the tumor had small uniform neoplastic epithelial cells growing with papillary structures and myxedematous stroma compatible with the diagnosis of SPN (Fig. 4B). Microscopic invasion to the portal vein (Fig. 4C) was also observed. An immunohistochemical staining study showed positivity for β-catenin and focally demonstrated positivity for synaptophysin. The labelling index of Ki-67 was <1%. The patient was discharged from the hospital 13 days after the operation without any complications. She has remained well without any signs of recurrence for over 2 years of follow up.

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Discussion

Ruptured SPN was first reported by Bombí et al⁷ in 1983. They treated a case of SPN presenting with acute abdominal pain and hemoperitoneum. From this literature onward, and to the best of our knowledge, there have been 16 case reports of ruptured SPN written in English, including ours. Among these, tumor rupture occurred at a primary lesion in 14,^7–19 and at a recurrent lesion (lymph node, liver metastasis) in 2 cases.^20,21 We summarized the clinical characteristics of 14 cases of ruptured SPN at a primary lesion (Table 1). Among these, SPN rupturing into an adjacent organ was only seen in our case. Although the chief complaint was pain or shock due to hemoperitoneum in most reported cases, our patient had no symptom except for low-grade fever. Most likely this is because the contents of SPN tumor had not leaked into the peritoneal cavity. Spontaneous rupture was observed in 8 while traumatic rupture was seen in the remaining 6. The tumor was located at the pancreatic head in 3 cases and at the distal part, including pancreatic body or tail in 11 cases. In so far as the 8 cases that spontaneously ruptured, the tumor was located at a distal part in 7 cases while at the head only in our case. Thus, our case was extremely rare in 2 respects. First, SPN was ruptured into the duodenum, not into peritoneal cavity. Second, the spontaneously ruptured SPN was located at the pancreatic head. The median diameter of the tumors was 11.0 cm (range: 4–17 cm). Apparently, it was larger than the tumors reported in a thorough review, which revealed that the mean diameter of SPN was 6.08 cm (range: 0.5–34.5 cm).²² This might be associated with a correlation between SPN size and tumor aggressiveness, which was demonstrated by Kang et al.²³

Table 1 Reported 14 cases of ruptured SPN at primary lesion

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Our case should be distinguished from other ruptured SPN cases regarding one more point: the involvement of adjacent organs including the duodenum and portal vein. Microscopically, SPN cells are known to delicately infiltrate into the surrounding pancreatic tissue, entrapping acinar cells and islets, although this tumor was grossly well demarcated from the normal pancreas.³ However, it is also known that vascular invasion is rare. Papavramidis²² reported that invasion to portal vein was observed in only 26 of 497 patients with data available regarding metastases or invasion. Cheng et al⁵ demonstrated 10 cases of adjacent organ (SMV/PV or left kidney) resections for SPN not leading to postoperative mortality. They showed that 9 patients with microscopically negative margins survived without any recurrence and metastasis while only 1 patient with a microscopically positive margin developed liver metastasis. They concluded that en bloc synchronous adjacent organ resection should be applied. Additional segmental resection of PV following wedge resection for positive margins in our case was proved valid based on this standpoint.

There are 2 clinical questions about the etiology of our special case. First, why did SPN of our patient rupture spontaneously? Since there have been only 8 case reports of spontaneously ruptured SPN, little is known about its pathogenesis. Takamatsu et al¹⁷ reported that SPN had a natural tendency to hemorrhage because the cystic part of it consisted of the degeneration following the intramural hemorrhage. Therefore, they concluded that the spontaneous rupture resulted from both abrupt massive hemorrhage and the increased pressure in the tumor. Second, why did it rupture into the duodenum and not into the peritoneal cavity as with all of other reported cases? It might have been because most of the cystic part of the tumor existed close to the duodenum while the solid part existed on the peritoneal side. Moreover, the wall of the duodenum might have been fragile due to tumor invasion. From the above, we considered that the pressure in the SPN had increased, perhaps due to sudden hemorrhage. Fortunately, the cystic part of the tumor located adjacent to the duodenum subsequently ruptured, breaking the weak wall of the duodenum.

Little is known about the prognosis of ruptured SPN. Kim et al²⁴ asserted that the tumor rupture might be a risk factor for recurrence after surgery for SPN. Indeed, recurrence was observed in 3 (21.4%) out of 14 ruptured SPNs. It was a higher incidence than that found in previously reported unruptured and completely resected SPNs.^24,25 On the other hand, peritoneal recurrence was evident in only 1 of 14 patients. Thus, the cause of the highly recurrent incidence of ruptured SPN might be associated with potential tumor aggressiveness rather than peritoneal dissemination. As for our patient, although the leaking of SPN contents into the peritoneal cavity was not developed, we still must pay close attention for recurrence. It is possible that the SPN cells had an aggressive nature because they invaded adjacent organs (duodenum and portal vein) and ruptured spontaneously.