Introduction

Solid pseudopapillary tumor (SPT) of the pancreas is a relatively rare neoplasm and represents < 1% of pancreatic tumors. It is more common in young patients, particularly in women. The course of the disease is generally insidious; tumor markers are normal and no metabolic disorder shave been reported. When symptoms occur, patients complain of epigastric pain, abdominal bloating or postprandial fullness¹. The diagnosis is based on the clinical presentation associated with imaging tests as ultrasound (US), computed tomography (CT) scan, magnetic resonance imaging (MRI) and endoscopic ultrasound (EUS). This tumor has generally been considered as a low-grade malignant neoplasm; therefore, surgery is the treatment of choice. Survival after complete surgical resection is 90% at five years and the incidence of liver metastasis is rare².

The aim of this study was to analyze nine patients with SPT of the pancreas treated in our department.

Material and methods

We conducted a retrospective, single-center study of nine patients with pathological diagnosis of SPT of the pancreas treated between February 2013 and September 2019. The following variables were analyzed: age, sex, tumor location, surgical treatment, operative time, complications, length of hospital stay and long-term follow-up. The complication were evaluated according to the Clavien-Dindo classification; those complications clinically relevant (grade > III) were considered for the analysis. All the statistical calculations were performed using SPSS (Statistical Package for the Social Sciences) 20.0 software package.

Results

All the nine patients were women and mean age was 30 years (range: 20 - 70). Epigastric pain was the main reason for consultation and all the patients underwent US, contrast-enhanced CT scan and gadolinium-enhanced MRI. The tail of pancreas was the most common location (n = 4; 45%), followed by the body (n = 2) and head (n = 2). (Table 1).

Table 1 Epidemiologic characteristics, location, size and clinical presentation 

Surgery was performed in all the cases. A laparoscopic approach was used in 60% (n = 5) of the patients after discussing the case in an interdisciplinary meeting. Spleen-preserving distal pancreatectomy was the most common strategy (n = 6), followed by cephalic pancreaticoduodenectomy (CPD; n = 2), and one patient with advanced disease underwent intraoperative biopsy. Operative time was 306 + 123 minutes. None of the patients required transfusion of blood products or vascular resection. There were no conversions to open surgery. Mean length of hospital stay was 5 days (range: 2-12) (Table 2). The pathological report confirmed the diagnosis of SPT. Five cases had a mixed pattern while the solid pattern was predominant in two and the papillary pattern in the other two cases. One of the tumors with a predominant solid pattern was unresectable due to liver metastasis.

Table 2 Surgical treatment, complications, hospital stay and readmission 

Three patients developed complications: two were clinically relevant (CD > grade III, 22%) and the patients had to be readmitted due to an abdominal collection that required percutaneous drainage. In both cases the diagnosis was pancreatic leak. Mean length of hospital stay after readmission was 6 + 3 days in these patients. In the remaining case (CD grade II) length of hospital stay was longer (12 days) due to delayed gastric emptying after CPD. Mean follow-up was 7 years. So far, 8 of the 9 patients are free of recurrence and the patient with unresectable tumor was lost of follow-up 26 months after the biopsy.

Discussion

Solid pseudopapillary tumor of the pancreas is a rare neoplasm and was first described by Franz Gruber in 1959. It represents < 1% of pancreatic tumors and 12% of pancreatic cysts. In a review by Ocampo et al., of 289 pancreatic resections the pathological examination reported a benign tumor in 38% of the cases; the diagnosis was SPT in six patients³. This tumor is more common in young (mean age: 20 years) women (90%; female to male ratio = 10:1). Complete resection is almost a synonym of cure. Metastasis occurs in 1% of the cases and involves the liver, portal vein, spleen, lymph nodes, omentum, duodenum, large intestine, lung and retroperitoneum⁴. The most common locations of the tumor are the body and the tail of the pancreas. Garcia Hevia et al. reported six cases located in the body and tail; multiple locations have also been described^5,6.

These tumors may develop from pluripotent pancreatic stem cells mediated by genetic factors. Other theory suggests that female hormones may play a role in these tumors as they are more prevalent in women. In addition, the presence of estrogen and progesterone receptors has been reported⁷. Tumor size is usually variable and has slow growth, with a doubling time of about 765 days, but may be large in some cases with local invasion and possibility of metastasis. Occasionally, tumor capsule rupture may occur producing hemoperitoneum and acute abdomen. In general, symptoms will depend on the time of progression, ranging from asymptomatic cases to those with symptoms due to compression, abdominal pain, bloating and a large palpable abdominal mass. Vega et al. reported four cases in which the chief complaint was abdominal pain and palpable mass⁸. Bile duct involvement is rare in tumors of the head of the pancreas (4%)⁹

Although SPT of the pancreas behave like a benign tumor, is considered a neoplasm of low-grade malignant potential. The pathognomonic histological findings are clusters of papillary cells with vascular cores surrounded by a mucinous stroma and a third layer of monomorphic cells. Histologically, it constitutes a low-grade carcinoma capable of producing metastasis characterized by solid areas which alternate with a pseudopapillary pattern, cystic spaces and areas of hemorrhage (Figure 1).

Figure 1 Light microscopic examination. Section of a solid-cystic tumor stained with haematoxylin and eosin (x40) showing the characteristic pseu dopapillary pattern. 

The preoperative diagnosis is made by imaging tests as CT scan and MRI. In contrast-enhanced CT scan, SPT of the pancreas appears as a well-limited mass with heterogeneous density due to the presence of cystic spaces and areas of necrosis and hemorrhage. The capsule may present calcifications. In MRI, the tumor appears as a well-defined isointense lesion on T1-weighted images or discrete hyperintensity on T2-weighted images. The cystic areas appear as hyperintense on T1 and T2, although occasionally they may appear as mixed areas of hyperintensity and hypointensity on T2-weighted images (Figures 2 and 3) In addition, a lesion with mixed cystic and solid appearance can be seen on CT scan or MRI in most cases. Three types of presentation are possible, solid, mixed (solid-cystic) and cystic. The mixed type is the most common¹⁰.

Figure 2 Fat-suppressed T1-weighted MRI of the abdomen (axial section). A rounded solid-cystic lesion with well-defined border is seen in the head of the pancreas with hyperintense and hypointense density. 

Figure 3 Magnetic resonance imaging in T2 sequence (axial section). A roun ded solid-cystic lesion with well-defined border is seen in the head of the pancreas with hyperintense and hypointense density. 

Endoscopic ultrasound has a sensitivity between 85% and 90% and specificity of 85%-96%, and provides the possibility of guiding fine-needle aspiration (FNA) with high diagnostic accuracy and a low risk of complications (1%) as pancreatitis, abdominal pain, vomiting and bleeding⁷.

The differential diagnosis should include other cystic tumors. Pancreatic pseudocyst is the most frequent cystic lesion; serous cystoadenoma usually occurs in older women and has a generally cystic appearance; cystic pancreatic mucinous neoplasm is characterized by thin septated cysts which provide a macrocystic appearance; and pancreatoblastoma which is common in childhood, predominates in male sex, is very aggressive and metastasizes at the moment of the diagnosis¹¹.

Parenchymal-sparing surgical resection is the treatment of choice. The surgical technique will depend on tumor location: Distal pancreatectomy with splenectomy or spleen-preserving distal pancreatectomy is indicated in SPT of the body or tail of the pancreas while CPD is indicated in those of the pancreatic head. Video-assisted laparoscopy is the recommended approach, but depends on the skills of the surgical team, the environment and the characteristics of the patients and tumor. When choosing the laparoscopic approach, it is important to bear in mind that the possibility of rupture is higher in large tumors, increasing the risk of dissemination, implantation and local recurrence.

The prognosis of the disease is favorable due to its low rate of malignant transformation and low probability of recurrence (6.6%). Metastasis occur in about 15% of the cases, but as the clinical progression of the lesions is slow, the five-year survival is > 90%, even in the presence of disseminated disease. Surgical resection is indicated for solitary liver metastasis, but treatment of multiple metastases is not well established. Chemotherapy, radiotherapy, arterial chemoembolization and radiofrequency ablation have been used. Dovigo et al.¹⁰ reported a case in which liver transplantation was performed with survival free of recurrence at one year. Sumida et al.¹² reported the case of a 14-year-old girl with liver metastasis who underwent successful split-liver transplantation (segments II-III) and was free of disease two years later.

Mortality is approximately 1.5%; risk factors for adverse outcome include perineural or vascular invasion, significant nuclear pleomorphism, increased mitotic activity, diffuse growth pattern, extensive necrosis and significant nuclear atypia. In 2012, Kruget al.¹³, published a case report successfully treated with selective internal radiotherapy (SIRT) in a patient with hepatic recurrence after resection of hepatic metastases. Four years after SIRT and 10 years after surgery the patient was in a good condition without any evidence for hepatic recurrence.

Conclusion

Frantz’s tumor is a rare neoplasm. The diagnosis should be suspected in the presence of a pancreatic tumor in young women. This tumor of low malignant potential can be cured after parenchymal sparing resection.