A CASE OF SOLID PSEUDOPAPILLARY TUMOR OF THE PANCREAS

: Solid pseudopapillary tumor of the pancreas is considered to be a rare pancreatic tumor. These tumors are typically present in women in their third decade of life with low malignant potential. We report a case of 42-year-old female who presented with intermittent abdominal pain of 3 months duration. Ultrasound and CECT showed mixed solid and cystic lesion of the body of pancreas. Distal pancreatectomy with splenectomy was done as a definitive treatment. The HPE was reported as SOLID PSEUDOPAPILLARY TUMOR. The case is presented for its rarity the importance of accurate diagnosis and treatment is emphasized.


INTRODUCTION:
Solid Pseudopapillary Tumor (SPT) of the pancreas is a very rare entity with a reported incidence of 0.13% to 2.7% of all pancreatic tumors, which was once described in many other terms, such as Frantz's tumor, solid and cystic tumor, papillary cystic neoplasm and solid and papillary epithelial neoplasm.

CASE REPORT:
A 42 year old female presented with complaints of vague upper abdominal pain associated with dyspepsia for 3 months. She had no jaundice, vomiting and loss of weight or appetite.She was not a known diabetic. On physical examination, there was tenderness in epigastrium and right hypochondrium. There was no mass or organomegaly. Her CBC, RFT, LFT, serum amylase and lipase were normal. Blood levels of tumor markers namely CEA and CA 19-9 were also normal. An ultrasound of the abdomen and pelvis showed a well defined solid cystic mass measuring 7.2*6.9 cm possibly arising from the head of pancreas. Upper GI endoscopy showed normal study. CECT of the abdomen and pelvis showed well defined cystic lesion measuring 8*8.4*8.9 cm arising from the body of pancreas with calcified walls and eccentric mural nodule with moderate enhancement (Fig 1,2).

Department of General Surgery, STANLEY MEDICAL COLLEGE AND HOSPITAL
After discussion in the tumor board an exploratory laparotomy was planned. Per operatively a mixed solid cystic lesion measuring 8*9 cm arising from the body of pancreas with no deposits in the liver/ peritoneum, no ascites (Fig 3). Distal pancreatectomy with splenectomy was done (Fig.4). Cut section of the tumour showed areas of haemorrhage and necrosis (Fig.5). Postoperative period was uneventful. The patient however developed diabetes mellitus and was started on human insulin. The histopathology was reported as pancreatic neoplasm composed of pseudopapillae with extensive areas of necrosis and hyalinisation and few psammoma bodies consistent with solid pseudopapillary tumour (Fig.6).Due to nonavailability in our institution,Immunohiistochemistry (IHC) was not done.

DISCUSSION:
Solid pseudopapillary tumor is an uncommon neoplasm that mainly occurs in women in the second to fourth decades of life. These neoplasms account for 5% of cystic pancreatic tumors and 1-2 % of exocrine pancreatic neoplasms. There have been 718 (1) cases reviewed in the English literature. It is characterized by low potential for malignancy and a favorable prognosis. The incidence of malignancy is as low as 15 % . Frantz described this tumor in 1959 as a "papillary tumor of the pancreas, benign or malignant". (2) Various   Fig 6: Histopathology showing psedopapillae NOMENCLATURE used are solid and cystic tumor , solid and papillary epithelial neoplasm, papillary-cystic neoplasm, papillary cystic epithelial neoplasm, papillary-cystic tumor, Franz tumor. In 1996, the World Health Organization renamed this tumor-solid pseudopapillary tumor and classified it to be arising from exocrine pancreas. (3) Patients usually are asymptomatic or may present with vague upper abdominal discomfort ,or an enlarging mass. On clinical examination the abdomen is usually non tender.Rarely obstructive symptoms may develop if the tumor causes compression of adjacent structures. (4) The serum biochemisry is normal (serum amylase and lipase) and negative for tumor markers (C 19-9,CEA,AFP).The diagnosis is mostly made incidentally or during evaluation for abdominal pain. CT scanning is the most frequent technique in diagnosing a solid pseudopapillary tumor . But an Endosonography may provide fine-needle puncture biopsy with an option of preoperative pathologic diagnosis of the tumor. (5) CT scan usually shows well encapsulated mass with solid and cystic areas due to haemorrhage. (6) Solid areas are more peripherally placed while the cystic areas are placed centrally. (7) SPT has distinctive pathological fratures. The mass may arise anywhere in the pancreas but most commonly in the head or tail.On gross examination the mass usually large(mean maximum dimension 9.3cm),well encapsulated with significant areas of haemorrhage ,necrosis and cystic change. Both a capsule and intratumoral hemorrhage are important clues to the diagnosis. Microscopically there are two types of cellular arrangements -solid and papillary. The hallmark histological patern occurs when tumor cells form papillary configurations composed of fibrovascular stalk surrounded by several layers of eopithelial cells. Solid a r e a s c o n t a i n i n g n e c r o s i s , f o a m y macrophages,cholesterol granulomas and calcifications may be seen. (8) Theories of histogenesis include a ductal epithelial, neuroendocrine, multipotent primordial cell, or even an extra-pancreatic genital ridge angle-related cell origin.Immunohistochemistry is usually positive for vimentin, CD10, CD56, and alpha-1-antitrypsin (2) . These cells may also reveal focal immunoreactivity for cytokeratin, neuron-specific enolase and synaptophysin.The role of progesterone in the growth of the tumor has been evidenced by progressive increase in tumor size with the continuation of pregnancy. (9) Because the tumor is usually surrounded by a pseudo-capsule and exhibits benign or low-grade malignancy, conservative resection with preservation of as much pancreatic tissue as possible is the treatment of choice. In most of he cases since the tumor arises from body of pancreas, distal pancreatectomy with splenectomy is the treatment of choice. Adjuvant therapy is used only in a small number of patients because of the high respectability and benign nature of SPT. (10) It is classified as TYPICAL SOLID PSEUDOPAPILLARY TUMOR, ATYPICAL SOLID PSEUDOPAPILLARY TUMOR, SOLID PSEDUPAPILLARY CARCINOMA . (11) Typical Solid Pseudopapillary Tumor: The classic CT features of solid pseudopapillary tumor are a large well-encapsulated mass with varying solid and cystic components caused by hemorrhagic degeneration. Calcifications and enhancing solid areas may be present at the periphery of the mass.
Atypical Solid Pseudopapillary Tumor: They may present with following atypical features. Solid Pseudopapillary Tumor with Metastasis to the Liver : Liver metastatic lesions can be multiple, but are generally solitary and may be amenable to resection .Cross-sectional imaging is helpful in the evaluation of liver metastasis to visualize local invasion of surrounding organs and blood vessels.

Solid Pseudopapillary Tumor with Ductal Obstruction:
Ductal obstruction and secondary pseudocyst formation are rarely seen in solid pseudopapillary tumors. Their presence in elderly patients may prompt a provisional diagnosis of ductal cell carcinoma.

Solid Pseudopapillary Tumor with Dense Calcification:
Although it is rare in solid pseudopapillary tumor , peripheral curvilinear calcification is sometimes seen on radiographs and CT scans . Central, stippled, eggshell calcifications have been reported.

Solid Pseudopapillary Tumor in Male Patients:
Solid pseudopapillary tumors in men may present a diagnostic problem because they are most commonly seen in young women. The male to female ratio is 1:9.5 Although solid p seudopapillary tumors rarely occur in men, the images are similar to those in women.

SOLID PSEUDOPAPILLARY CARCINOMA:
The incidence of malignancy is 15%. (8) They are more common in older age group and have male preponderance. (8) Features suggestive of malignancy in SPT are angioinvasion, perineural invasion, deep invasion of the surrounding pancreatic parenchyma, metastasis. Venous invasion, high nuclear grade and "necrobiotic nests" predict the possibility of malignancy in papillary cystic neoplasm. (12) Capsular invasion serves as a prognostic indicator for SPT. (13) CONCLUSION: Solid pseudopapillary tumor of the pancreas is a rare condition with a low potential for malignancy. These tumors usually affect women in the second or third decades of life. The prognosis is favorable even in the presence of distant metastasis. Although surgical resection is generally curative, a close follow-up is advised in order to diagnose a possible local recurrence or distant metastasis. Overall 5year survival is as high as 97% in patients undergoing surgical resection with disease free survival as high as 21 years. (8)