A number of rarer pancreatic carcinomas exist. These include acinar cell carcinoma, intraductal carcinomas, and cystic carcinomas.
Acinar Cell Carcinoma
About 1% of pancreatic tumours are acinar cell carcinomas. There is a similar age range to ductal adenocarcinoma. Tumours tend to have pushing rather than infiltrative borders, causing obstructive jaundice less frequently than typical ductal carcinomas. These tumours can also produce high quantities of lipase which is secreted into the bloodstream, leading to polyarthralgia and subcutaneous fat necrosis.
The tumours are often large and nodular macroscopically. On microscopy, cells are arranged into small glandular structures. Immunohistochemistry is helpful in demonstrating pancreatic enzyme production. On electron microscopy, secretory granules are visible.
Distant metastases are common at diagnosis and 5 year survival is less than 10%.
Cystadenoma and Cystadenocarcinoma
Cystadenoma is a benign tumour that accounts for about 1% of pancreatic tumours. They can cause abdominal pain but a signficiant number are found incidentally. Macroscopically, they consist of sponge-like tissue filled with small cysts containing serous fluid. Malignant transformation is rare with few cases described.
Mucinous cystadenoma and mucinous cystadenocarcinoma
Another rare tumour that accounts for 1% of pancreatic neoplasms. Instead of the serous fluid seen in cystadenoma, mucinous cystadenomas often contain a single cyst filled with thick mucinous material. Malignant transformation can occur and resembles ductal adenocarcinoma.
Intraductal papillary-mucinous neoplasms
Intractual papillary-mucinous neoplasms make up another 1% of pancreatic tumours. They usually occur in the main pancreatic ducts and cause pain and jaundice. Imaging demonstrates dilatation of the distal pancreatic duct. Survival is good due to the early detection of the tumour.