Solid pseudopapillary tumour of the pancreas in a child : case report

Introduction Solid pseudopapillary tumour of the pancreas, though rare, is a low-grade malignancy with indolent behaviour. It is encountered predominantly in young females, although it has been seen in males and children. Most patients present with vague non- specificabdominalpainresultingin� delayed diagnosis. Therefore diagno- sis of this tumour may be an inciden- talfindingduringdiagnosticimaging� procedures or maybe assumed when a young women presents with an asymptomatic palpable mass. Traditionally the presence of a large bulky pancreatic tumour in a child should raise suspicion of the diagno- sis of pancreotoblastoma. This study reports a case of a solid pseudopapil- lary tumour of the pancreas in a child. Case report We present a case of an eight-year-old child presenting with pain and a lump in the epigastric region. Computerised tomography was subsequently per- formed to localise the mass accu- rately. Computed tomography showed a minimally enhancing solid mass in the head and proximal body of the pancreas compressing the second and third part of the duodenum and measuring 7.2 × 6.9 × 6.4 cm. Conclusion This case report highlights the fact that with characteristic imaging fea- tures the diagnosis of solid pseudo- papillary tumour of the pancreas should be considered irrespective of theageprofileofthepatient.


Introduction
Solid pseudopapillary tumour (SPT) of the pancreas is rare and often suspected in young females who present with pancreatic mass accounting for less than 2% of exocrine pancreatic neoplasm 1,2 .SPT commonly occur in women in the second to fourth decade of life and is rare in children.It is thought to arise from cells of the endocrine pancreas, though some investigators have postulated their origin from the exocrine pancreas 3 .These tumours generally go undetected till they grow to a large size.Despite this presentation these tumours show low malignant potential and rarely metastasise.Therefore, surgical excision offers an excellent prognosis even in large or metastasising tumours 1 .Despite a few citations it is worthwhile to note that SPT may present on the odd occasion as an acute abdomen with sudden onset of pain due to compression upon the adjoining organs 4 .SPT shows different clinical features in childhood.High survival rates can be achieved in most cases, warranting aggressive treatments even in metastatic disease 5 .A meticulous radiological survey prior to any surgical intervention may aid in the timely diagnosis of this condition.This study is an attempt to highlight the importance of imaging modalities such as CT scan and ultrasonography (USG) in particular, in the diagnosis of SPTs of the pancreas.

Case report
An eight-year-old female child presented to paediatric OPD with complaints of pain and a lump in the epigastric region for four months.Routine haematological and biochemical parameters were normal.On physical examination, patient was mildly cachexic.A non-tender slightly mobile epigastric mass, measuring 5 × 7 cm was palpable.On clinical test (decubitus, knee-elbow position) it was suspected to be of retroperitoneal origin.USG done on Philips 4000 showed a well-defined homogenously hypoechoic, smoothly margined mass with a few necrotic areas in the epigastric region.The mass was inseparable from the pancreas.Adjacent visceral structures were normal with duodenum closely abutting the mass (Figure 1).

Solid pseudopapillary tumour of the pancreas in a child: case report
MK Mittal 1 , NK Jha 1 , V Mehta 2 *, RK Suri 2 , M Sinha 1 , NK Bhambri 1 , BB Thukral 1 Surgery   Colour Doppler investigation revealed the mass to be avascular and displacing adjacent portal vein, SMA and splenic vein (Figure 2).Both plain and contrast CT abdomen were performed on Siemens Emotion 6 machine.It revealed a minimally enhancing solid mass in the head and proximal body of the pancreas compressing the second and third parts of the duodenum and measuring 7.2 × 6.9 × 6.4 cm.No calcificationorhaemorrhagewasseenon plain scan, though a few necrotic areas and peripheral capsular enhancement was present.Splenic vein and superior mesenteric vein were compressed by the mass just short of their confluence.Inferior vena cava and aorta with their major branches were found to be normal.The common bile duct (CBD) and pancreatic duct were not dilated (Figure 3).
MRI on Philips 1.5 T Achieva unit was done for further anatomical and morphological characterisation of the lesion.It was hypointense on T1WI and hyperintense on T2WI compared to pancreatic parenchyma and showed a thin hypointense capsule (Figure 4).Postcontrast study showed minimal enhancement of the mass and moderate enhancement of the capsule.Magnetic resonance cholangiopancreatography revealed normal calibre of the CBD and MPD.The MPD was displaced superiorly by mass and was not visualised in its mid-course but seen normal distally.Therefore, it was inferred that the mass is displacing rather than encasing the MPD (Figures 5 and 6).
Pancreatoblastoma was kept as thefirstdiagnosisinviewofthesolid nature of mass and age of the patient.SPT was kept as second possibility even though the age of the patient was not in favour, based on CT and MRI imaging features like presence of true capsule, paucity of necrosis relative to tumour size, minimal enhancement of the mass with good capsular enhancement and patchy foci of T1W hyperintensity within the mass suggesting haemorrhage.
Surgical exploration of the tumour was performed which revealed a 7 cm diameter pancreatic mass arising from the head and proximal body of the pancreas displacing the duodenum anterolaterally.The major blood vessels were displaced.The tumour was in close relationship with MPD, so along with tumour resection a Whipples procedure was carried out (Figure 6).Postoperative course was uneventful.Histopathology confirmed the diagnosis of SPT of the pancreas.

Discussion
SPT of the pancreas is a rare tumour and only 700 reports have been reviewed in the literature since it was first described by Frantz 6 in 1959.The tumour has been known by a number of synonyms including Frantz's tumour, solid and cystic acinar tumour, papillary epithelial neoplasm, and solid and papillary epithelial tumour or neoplasm.In 1996, the World Health Organization recognised the designation 'solid pseudopapillary tumour' as a distinct tumour of the exocrine pancreas 7,8 .
SPT is most commonly diagnosed in adolescent girls and young women, and a predilection for Blacks and East Asians has been suggested.Most patients with SPT are brought to medical attention in the second decade of life.Female patients account for 83%-98.5% of the reported cases.Controversies regarding the role of genetic or hormonal factors in the causation of the tumour to explain the strong female predilection are present.Some authors in the past have denied it 9 whereas others have agreed to it strongly 4 .
Zhou et al. 10 have suggested that SPT may represent the most common pancreatic tumour in Asian children.
SPT is a slow-growing tumour and hence the majority of patients present with vague abdominal symptoms, resulting in a delay in presentation and diagnosis.It is commonly large and circumscribed or encapsulated, with haemorrhagic changes.The tumour is usually round to ovoid and solitary and can occur in any part of the pancreas, although some investigators have observed a predilection for the tail 11 .
The tumour is thought to be ductal or acinar in origin.The tumour exhibits typical features on light microscopy.The cystic appearance on gross examination may present a diagnostic dilemma with cystic neoplasm of the pancreas.Immunophenotyping has been used to differentiate these tumours from other pancreatic neoplasms.SPTs show positive tests for vimentin, neuron-specific enolase, α 1 -antitrypsin and α 1 -antichymotrypsin, and are negative for chromogranin, epithelial membrane antigen, and cytokeratin, insulin and glucagon 3,12 .Cytological smears are highly cellular and show monotonous population of small cells arranged in aggregates and papillae with fibrovascular cores 3,12 .There are no clear histological features, which establish the clinical behaviour of these neoplasms.The tumours exhibit low-grade  malignant potential and metastasise infrequently 13 .The imaging features ofSPTreflectthepathologicfindings of cystic and solid components, intratumoural haemorrhage, a fibrous capsule and, less commonly, calcification.When present, the fibrous capsule and internal haemorrhage are the features that distinguish SPT from other pancreatic tumours 10,12 .
USG and CT show a large wellcircumscribed mass with quite variable appearance depending on its composition.Tumours compress adjacent structures rather than invading them.CT shows solid portions of the mass to be iso to hypoattenuating to the pancreas and that of cystic components slightly hyperattenuating than gallbladder due to the presence of blood products and debris.Calcification is seen in onethird of the cases with only minimal enhancement 10,12 .
MRI shows hypointense fibrous capsule and internal haemorrhage (seen as high-signal intensity on T1W images) and is very characteristic of SPT.Solid portions of the tumour are iso to hypointense to pancreas on T1-weighted images and slightly hyperintense to pancreas on T2-weighted images.Early peripheral, heterogeneous enhancement greater than that of the adjacent pancreasandsometimesprogressivefillin on dynamic-enhanced images are seen 12,14 .
Angiography of SPT is avascular to hypovascular and displaces vessels.Local recurrence has been reported in less than 5% of the cases.Metastases typically occur in the liver, lymph nodes and peritoneum.Because these tumours rarely invade adjacent structures, even large tumours have been shown to be resectable.Rarely vascular invasion of the superior mesenteric artery or portal vein are encountered and may limit resectability.Complete resection of local disease is curative.Even patients with residual disease or metastases have been reported to have long-term survival following surgical treatment.Very few reports show the use of chemotherapy or radiotherapy for these tumours with only a limited response 13,15 .

Differential diagnosis
SPT needs to be differentiated from pancreoblastoma which is a common paediatrictumourinthefirstdecade.Various differentiating features are presented in Table 1.
Other differential diagnoses include functional endocrine tumour (enhances avidly postcontrast and are small in size), acinar cell tumour, ductal adenocarcinoma (patients are in the older age group), lymphoma (homogenous enhancing mass with bulky lymph nodes), lymphangioma, dermoid cyst and peudopancreatic cyst (appears as a multiseptated cystic lesion on USG with none to minimal peripheral enhancement), primitive neuroectodermal tumour and mesenchymal tumours (heterogeneous and infiltrating margins) 10,12 .

Conclusion
The possibility of SPT should always be kept in a child who presents with large bulky pancreatic mass and characteristic imaging features.Because of the indolent nature of these tumours and the low malignant potential, aggressive attempts at complete surgical resection are warranted.Large tumours are usually resectable and size does not predict the outcome.Surgical bypass may be the only feasible option in patients with large tumours where the risks of attempting resection or debulking may be associated with overwhelming morbidity.

Capsule with internal haemorrhage
The tumour appears multiloculated with enhancing septa

Figure 1 :
Figure 1: USG with colour Doppler showing avascular epigastric region solid mass with compression of splenic and portal vein and displacement of adjacent arteries.

Figure 2 :
Figure 2: CECT abdomen showing minimally enhancing pancreatic mass with noevidenceofcalcification.Peripheralcapsularenhancementisseen.Adjacent visceral structure and vessels are displaced by the tumour.

Figure 3 :
Figure 3: Axial T2W SPIR image showing hyperintense mass with hypointense capsule.Minimal area of patchy cystic degeneration seen.Adjacent bowel loops are displaced by the mass.CBD shows normal calibre.

Figure 4 :
Figure 4: Precontrast T1W image showing shows well-defined, smoothly marginated pancreatic mass with hypointense capsular rim.Hyperintense foci of haemorrhage are also seen within the mass.

Figure 6 :
Figure 6: Preoperative image showing well-encapsulated mass free from adjacent structure.

Figure 5 :
Figure 5: Postcontrast T1W image showing minimal enhancing mass with moderate peripheral capsular enhancement.Aortic pulsation artefact also noted.