Case Report: Solid pseudo-papillary tumor of the pancreas

Introduction

A solid pseudo-papillary tumor (SPT) of the pancreas is a rare pathological entity accounting for approximately 2% of pancreatic exocrine tumors.^1,2

Its pathogenesis is still discussed. Clinical symptomatology is not specific and the discovery may be fortuitous. The diagnosis of this tumor is histological. The treatment is exclusively surgical associated with a good prognosis.^3,4

Observation

A 19-year-old African woman, a high school student with no history of abdominal trauma, surgery or smoking was hospitalized for the exploration of an abdominal pain in the epigastrium and the left hypochondrium. She also had no specific family medical history. The pain started six months before admission and gradually got worse. It was associated with an alteration of her general state. She reported 11kg weight loss during this period.

The physical examination was uneventful except for a tenderness at the level of the epigastrium. Laboratory findings were normal. The abdominal Doppler ultrasound showed a round, well limited solid vascular mass. It was actually a large one measuring 42 mm and extending from the retroperitoneum down to the lower pole of the homolateral kidney. It was hyperechogenic and heterogeneous in appearance but mostly cystic in nature. A computed tomography (CT) Scan of the abdomen and the pelvis together with a pancreatic MRI revealed the presence of a 44×42×34 mm solid mass in the pancreatic tail. This mass was spontaneously isodense with a moderate and heterogeneous contrast enhancement and some scattered cysts. This mass presented regular contours with a predominantly lower extension reaching the descending colon without any symptoms of compression. The peritoneal fat was of normal appearance (Figure 1). The biological, hepatic and pancreatic check-up was normal. EUS-guided biopsy is not available in our hospital service, That’s why our patient underwent operation without a precise diagnosis before intervention. The surgical operation confirmed the existence of a large exophytic tumor (diameter: 5cm) appended to the lower edge of the pancreatic tail. There was no locoregional invasion or distant metastasis. Surgical resection of the tumor by partially cutting the pancreas was performed. The surgery was without complication. The histological examination revealed a solid pseudopapillary tumor of the pancreas. Indeed, the cyto-architectural aspects confirmed our diagnosis. An immuno-histochemical study showed the existence of CD10 tumor cells. The patient developed well in the postoperative period, with normal US (three, 12 and 24 and 48 months) and CT scans (12, 24 and 48 months) and no evidence of residual disease.

Figure 1. Abdominal magnetic resonance imaging showing a heterogeneous mass repulsing below the left kidney.

Discussion

Solid pseudo-papillary tumor (SPT) of the pancreas is a rare pathological entity first described by V. K. Frantz in 1959.⁵ This entity represents 0.7 to 2.7 % of all the exocrine pancreatic tumors and less than 5 % of cystic pancreatic tumors.⁵ The rarity of this neoplasm makes our case particular.

Less than 1000 cases have been reported in the literature, mostly in isolated cases. It is classically described in young females in more than 95% of cases with an average age of 22 years (from 2 to 85 years)⁶ as was the case of our patient. Rare cases in males and the elderly have also been reported.⁷ It was also frequently found in different ethnic groups such as Black and Asian people. Its etiopathogenesis is still unknown. Two diagnostic hypotheses were proposed. The first was based on the role of sex hormones due to the female predominance and the presence of progesterone receptors. The second was more directed towards an embryonic origin with a totipotent stem cell that would be transformed into an exocrine and endocrine pancreatic cell.⁸

The tumors were discovered in different circumstances. The revelation pattern was vague abdominal pain in 58% of cases. The discovery may be fortuitous on abdominal imaging performed for another reason. It may also be discovered incidentally on a routine examination.

The tumor can also be revealed as an abdominal mass or as a complication which can occur in the form of a compression of the digestive, biliary or vascular structures when the tumor becomes voluminous or in the case of an intra-tumor hemorrhage. These complications may be spontaneous or secondary to abdominal trauma (3%).^6,9

In our case, it was the abdominal pain which prompted the need for a follow-up imaging examination. There were no specific biological signs.

These tumors affect the head, body and tail of the pancreas, but develop preferably in the body and tail region (64% of cases).^5,10 Rare cases of extra-pancreatic localizations (retroperitoneum, retro duodenal, meso-colic and hepatic) have been described. These rare extra-pancreatic areas are suggestive of two etiopathogenic hypotheses: a development from ectopic pancreatic tissue, or a development from totipotent stem cells being transformed into pancreatic cells. Macroscopically, the tumor is often voluminous, 10 cm long on average. It can reach 25 cm in diameter. It is often rounded or oval, surrounded by a fibrous capsule.^1,11

On microscopy, the solid zones are composed of tumor cells of small size, monomorphic, cuboid or polygonal. A clear cytoplasm that is sometimes vacuolated and that contains diastase-resistant PAS-positive (periodic acid Schiff) globules can be seen. The nucleus is oval, regular, with peripheral chromatin condensations. The cells are arranged either as solid plaques or as a pseudo-papillary device with a fibrovascular axis bordered by a row of cells. Mitoses and cytotoxic atypia are an uncommon occurrence. Foamy histiocytes and giant cells can be found around cholesterol clefts.¹¹

The stroma is usually of the endocrine type. It is rich in blood capillaries. The anatomo-pathological criteria for malignancy are found in only 10 to 15% of cases (invasion of adjacent structures, arterial embolism, perineural invasion, and lymph node metastases that are regional or distant). In these cases, the SPTP is classified as solid pseudo-papillary carcinoma. SPTP immunohistochemical profile is variable. Typically, tumor cells are labeled with anti-CD10, alpha-1 antitrypsin, vimentin, NSE, E-caderin and beta-catenin antibodies. Anti-progesterone antibody labeling is also noted. The positive immuno-labeling of tumor cells for some endocrine markers may prove some endocrine differentiation.

Morphological explorations make it possible to study the characteristics of the lesion: its nature (solid, cystic or mixed), to specify the organ of origin, to study its features regarding the neighboring vessels and the organs and to look for metastases at distances.

Local invasion is reported in 15% of cases. Secondary sites were reported in 5% of the cases mainly affecting the liver.¹²

An abdominal ultrasound shows an echogenic and homogeneous mass, or heterogeneous with both cystic and solid zones.

An abdominal computed tomography (CT) shows a limited heterogeneous lesion that is rather hypodense. It is not very vascularized. It is also of mixed composition associating solid and cystic zones and is little or partially enhanced at the periphery after injection of the contrast agent. Signs of compression of the adjacent organs can be observed. The magnetic resonance imaging (MRI) shows a heterogeneous lesion with a hyper signal in T1 and T2. The capsule is often visible in the form of a hypo-intense border in T1.^13,14

An unequivocal diagnosis remains histological. Endoscopic techniques offer ways to diagnose pseudopapillary solid tumor of pancreas(SPTP) before surgery. Like abdominal ultrasound, SPTP can appear as solid, cystic, or a combination of both on endoscopic ultrasound (EUS). EUS-guided fine needle aspiration (EUS-FNA) is now commonly used to diagnose pancreatic tumors, with high accuracy rates of over 80%. This technique not only allows for biopsy but also enables the minimally invasive collection of fluid samples, such as pancreatic juice and cyst fluid.⁵

Regarding surgical technique, indeed Parenchyma-preserving pancreatectomies, such as enucleation, central pancreatectomy, and duodenum-preserving pancreatic head resection (DPPHR), are being performed more frequently.¹⁵

Studies have shown that these procedures can lower the occurrence of pancreatic endocrine and exocrine insufficiencies while maintaining positive short- and long-term results.¹⁵

The choice of the operating method depends on the tumor size, localization and the possible invasion of adjacent organs.

Enucleation, duodenum-preserving pancreatic head resection (DPPHR), and pancreaticoduodenectomy are options for SPTP located in the pancreatic head.¹⁶

Enucleation, central pancreatectomy, and distal pancreatectomy (with or without splenectomy) are available for tumors in the pancreatic body and tail.^17,18

Minimally invasive techniques, including laparoscopic and robotic surgery, can be suded in both traditional and parenchyma-preserving procedures.

To date, no consensus on the best approach for the treatment of SPTP metastasis has been established. Metastasis to lymph nodes is not common, occurring in only 1.0% to 7.9% of cases. Therefore, extended lymphadenectomy may not be needed for most patients.¹⁸

The excision should be extended in case of invasion of the neighboring organs and possible nodules of peritoneal carcinosis which must be resected. The presence of invasion of the portal or mesenteric veins should not contraindicate a curative treatment, as cases of portal or mesenteric resection have been reported with prolonged survival. Associated metastatic lesions should be resected with a reasonable risk, and tumor recurrences should benefit from a surgical excision.

Adjuvant therapy chemotherapy and radiotherapy has been shown to be effective. in some unresectable cases.^12,13

The prognosis is good even in cases of metastasis.⁵ Survival, up to 17 years, has been reported for metastatic tumors. Long-term survival after complete resection of a non-metastatic tumor is between 80 and 90%, but associated with a recurrence rate of 10 to 15%.⁹ No pathological criteria (vascular, perineural and ganglionic invasion or mitotic index) currently predict survival.

Conclusions

SPTP is a rare tumor with attenuated malignancy. Its diagnosis is based on histology coupled with immune-histochemistry. Surgery remains the treatment of choice even in the presence of metastases.