Unusual locations for a pseudopapillary tumour

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Unusual location for a pseudopapillary tumour

An unusual location for a solid pseudopapillary tumour

Abstract

Solid pseudopapillary tumours (SPT) are rare exocrine pancreatic tumours which most commonly occur in young women. Extra pancreatic SPT have been described to arise from the retroperitoneum, liver, omentum and mesocolon. Given their low mitotic index complete surgical resection provides the best prognosis.

We hereby present a case of a SPT arising from the right hemi-diaphragm, of a young female, without the presence of a pancreatic primary tumour. Our patient underwent an extensive resection including the right lower lobe, diaphragm and a segment of the liver. Histological resection was a complete. 18 months following the initial surgery she represented with pain and computed tomography confirmed recurrence. She has survived 3 years post resection.

We discuss this case and the typical presentation of SPTs and how this case provided a diagnostic challenge given its location. We stress the importance in a complete resection without the breach of the tumour. We discuss the use of chemo-radiotherapy in this case and emphasise the need for further research to better understand its role.

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Keywords: Cancer (Diaphragm), Diaphragm, Histology (Pseudopapillary tumour), Tumour (Diaphragm)

Introduction

Solid pseudopapillary tumours (SPT) are tumours typically found in the pancreas of young females [1]. They have been described in extra-pancreatic sites including the retroperitoneum, omentum, liver and mesocolon [2,3]. The indolent nature of these tumours favour surgical resection. We present a case of a pseudopapillary tumour centred on the right hemi-diaphragm with extension into the right hemi-thorax and abdomen. We emphasize the surgical considerations and discuss follow up strategy and management.

Case report

A 42 year old female ex-smoker presented with right sided chest pain. Computed tomographic (CT) scans and magnetic resonance imaging (MRI) revealed a massive lesion extending from the right lower lobe into the abdomen with suggested invasion of the right adrenal gland and right lobe of the liver (Figures 1 and 2). Prior to resection a laparoscopy was performed to further visualize the extent of mass and to obtain biopsies. Histology was not convincing however suggested a low-grade papillary tumour.

Due to the uncertainty and the low grade nature of the mass it was felt that chemotherapy would have a poor response and that a surgical resection would offer the best prognosis. She therefore underwent surgery involving an extended postero-lateral and subcostal thoracotomy to remove the right lower lobe, most of the right hemi-diaphragm, the right anatomical lobe of the liver and the right adrenal gland. All visible tumour was removed and though it was felt that the tumour did not directly invade the liver and lung these further resections were carried out to ensure clearance.

Macroscopically the tumour was well circumscribed weighing 2400 g and measuring 27 x 17 x 12 cm. The cut surface revealed a heterogeneous tumour with soft yellow friable tissue and large areas of necrosis with the occasional cysts. The tumour did not infiltrate the lung, skeletal muscle, liver or the adrenal gland.

Microscopic examination revealed proliferation of poorly cohesive cells which contain round nuclei and scanty cytoplasm. Occasional cells contained hyaline globules. An alveolar and papillary pattern was noted with areas of necrosis. The lesion was ill defined and tumour cells were present in adjacent lung parenchyma. The tumour was microscopically completely excised.

Immunohistochemistry showed positivity with CD99 (mic2) and CD56 markers. Tumour cells remained negative with all the epithelial markers tested, synaptophysin, S100, HMB45, Melan A, Desmin, SMA, Oestrogen receptor and progesterone receptor markers. Beta catenin immunostaining showed preserved membranous expression with no evidence of nuclear translocation. By contrast, E-cadherin immunostaining showed loss of membranous expression in 100% of tumour cells. Ki67 immunostaining showed positive nuclear staining in approximately 10% of the tumour cells.

Overall appearances were then (despite lack of beta catenin altered expression) highly suggestive of a solid pseudopapillary tumour centred on the right hemi-diaphragm. Importantly there was no ectopic pancreatic tissue seen. Histology suggested the tumour was fully resected therefore adjuvant therapy was not offered.

Eighteen months later she represented with chest pain and CT scan and biopsy showed recurrent disease with a similar histopathological profile. The CT scan suggested multiple foci of recurrence at around the chest wall. An extrapleural pneumonectomy was considered however this would not be curative and would carry an unacceptably high morbidity and mortality. Due to the low mitotic index and low Ki-67 this tumour was indolent and was anticipated to not respond to chemotherapy. The patient did undergo chemotherapy and radiotherapy for pain. As expected she had a poor response to chemotherapy however is alive 3 years post resection.

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Discussion-

We have here presented the case of a massive extra-pancreatic pseudopapillary tumour. Pseudopapillary tumours are rare lesions of the pancreas. Of all exocrine pancreatic tumours they account only for 1-2%. Greater than 90% of cases are in young females (4). There have been few cases reported of extra-pancreatic pseudopapillary tumours however many of these were felt to be derived from ectopic pancreatic tissue (3, 5). The sites described, other than the pancreas are; the mesocolon, liver, retroperitoneum and greater omentum.

These tumours usually present with abdominal pain or associated symptoms and signs of compression. As in our case serum tumour markers are typically negative. MRI is superior to CT due to their varying tissue characteristics such as cystic components, haemorrhage, necrosis and the presence of a capsule. Immunohistochemistry is invaluable as it is typically positive for vimentin and anti-trypsin whilst being negative for trypsin and chymotrypsin. The CD99 positivity and loss of E cadherin expression a pseudopapillary tumour remains the most likely diagnosis. Differential diagnoses include neuroendocrine tumours, sarcomas (EWS/ FLI1 Type 1 and 3), vascular tumours (CD34 and CD31) and melanoma (S110, HMB45 and melan A). In our case these other differential diagnoses were excluded by the immunostaining of the markers listed. Given its unusual location, centrally focused on the right hemi-diaphragm, it has been difficult to confirm whether this is ectopic tissue, a metastatic deposit or an unusual presentation of a primary diaphragmatic tumour. As previously mentioned imaging did not reveal another primary focus nor did histology suggest ectopic pancreatic tissue.

As these SPTs are rare and infrequently described in literature we have looked to the prognosis of pancreatic pseudopapillary tumours which are usually good following radical resection. This is due to the well encapsulated nature and the low grade malignant potential of the tumour type. A five-year survival rate of 97% has been reported [6]. Local recurrence rate of pancreatic pseudopapillary tumours have been reported at 6.2% while distant metastasis occurs in 15% of cases and presents following a disease-free interval of 8.5 years [7,8]. In our case recurrence occurred much sooner than anticipated however there are examples of tumours with low mitotic index that demonstrate an aggressive nature such as: neuroendocrine tumours of the gastrointestinal tract or lungs, gastrointestinal stromal tumours (GISTs) and liposarcomas [9]. Currently no histological markers exist to help predict the aggressive nature or prognosis. The distribution of the chest wall metastasis in this case is similar in theory to the transcoelomic spread of pseudopapillary tumours. This early and local recurrence could be explained by a potential breach of the tumour wall. Such breach is a known poor prognostic marker in GISTs [9]. As most of these types of tumours are fully resected adjuvant chemotherapy or radiotherapy is not offered. Due to this reason the role of such therapy is yet to be defined. As these tumours have a low Ki67 index, chemotherapy was therefore felt to have a limited role however this was offered as our patient was keen to attempt any avenue of treatment.

In conclusion, this is a case of an unusual location for an extra-pancreatic pseudopapillary tumour. In keeping with pancreatic pseudopapillary tumours this case was in a young female. As with those that arise from the pancreas this tumours was well encapsulated and we feel the best management option is for radical surgical resection. We stress the need to ensure breach of the tumour does not occur. Due to the low grade nature of these tumours recurrence is reported as rare and as in our case occurred at 18 months. For this reason we suggest long term follow up with a low threshold to repeat imaging. Further work needs to be carried out to define the role of neoadjuvant or adjuvant chemo-radiotherapy in pseudopapillary tumours.

Acknowledgments

None

Figure 1. Transverse computed tomographic scan at the level of the 8th thoracic vertebra. This shows the significant occupancy of the thoracic cavity by the diaphragmatic mass.

Figure 2. Coronal magnetic resonance image showing the occupancy of the thoracic and abdominal cavity by the diaphragmatic mass and its suggested involvement of the right kidney.

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