Year : 2005 | Volume
: 15 | Issue : 1 | Page : 35--40
Radiological features of rare pancreatic tumors.
R Subbaraidiu, S Patnaik
Department of Radiodiagnosis, Medwin Hospitals, Hyderabad, India
401, Rajyalaxmi Enclaves, 7-1-77, Dharam Karam Road, Ameerpt, Hyderabad 500 016
Ductal adenocarcinomas and its variants comprise 90 percent of all tumors of pancreas. The rest are rare. The radiological features of five such cases of rare pancreatic tumors are described and the relevant literature is reviewed.
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Subbaraidiu R, Patnaik S. Radiological features of rare pancreatic tumors. Indian J Radiol Imaging 2005;15:35-40
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Subbaraidiu R, Patnaik S. Radiological features of rare pancreatic tumors. Indian J Radiol Imaging [serial online] 2005 [cited 2019 Nov 19 ];15:35-40
Available from: http://www.ijri.org/text.asp?2005/15/1/35/28741
Pancreatic tumors rank as the fourth most common cause of cancer - related deaths in United States 1. Ductal adenocarcinoma and its variants comprise 90% of all tumors of pancreas. The rest of pancreatic tumors are rare but they present with distinct morphological and biological features needing our attention ,. In this article we report five such rare tumors of pancreas encountered at our hospital in the recent past.
Case 1 :
A fifteen year old female patient presented with vague abdominal discomfort with dyspepsia of two months duration. Routine abdominal radiograph and barium studies suggested a mass in retroperitoneum [Figure 1] Ultrasound examination confirmed a large mass of mixed echo-texture in the head and body of pancreas. Operative biopsy showed it to be solid cystic papillary tumor.
Case II : A eighteen year old female patient presented with an upper abdominal mass which on ultrasound examination was found to be a space occupying lesion in pancreatic head with mixed echo-texture. CT scan revealed the same mass and operative biopsy proved it to be a solid-cystic papillary tumor [Figure 2].
Case III :
A twenty-six-year-old female patient presented with pain abdomen for the last 4 months. Physical examination suggested a vague mass in upper abdomen. Ultrasound examination revealed well circumscribed, encapsulated, mixed echosenicity mass in the head and body of pancreas. CT Scan [Figure 3] A and B confirmed the same mass (size 7x6 x 5.5 cm). It had both solid and cystic areas. There was rim enhancement on intravenous contrast. There was no calcification. The liver and biliary system were normal. There was no lymphadenopathy. Surgical biopsy confirmed it to be a solid cystic papillary tumor.
Case IV :
A thirty-year-old male patient presented with recurrent pain abdomen and a large non-tender lobulated mass in epigastrium. Ultrasound and CT Scan (Fig. IV. A and B) revealed it to be a mass measuring 7x6x5 cm, confined to the tail of pancreas. It was a large encapsulated, multilobulated, non-homogeneous in appearance. On IV contrast, it showed inhomogeneous enhancement. The nodes at porta-hepatis were enlarged. Liver showed multiple hypodense nodular lesions (Fig. IV C). Multiple soft tissue density masses were seen along the anterior
abdominal wall. Chest CT revealed multiple nodules in both lungs (Fig IV D). CT guided FNAC of pancreas confirmed pancreatoblastoma.
Case V :
A 49 year old female presented with anorexia, loss of weight and pain abdomen for last 1 year. Ultrasound examination revealed a large cystic SOL (15 x 16 cms) with multiple internal septations in the body of pancreas. On CT examination the mass was found to be well circumscribed, hypodense with smooth external surface. There were daughter cysts inside the mass. The periphery of the mass was enhancing without any evidence of calcification. There was no peripancreatic or distant metastasis. Excisional biopsy proved it to be mucinous cystadeno-carcinoma [Figure 5].
The epithelial tumors of pancreas can be related to different cell components of the gland including duct, acinar, centro-acinar and endocrine cells. Histology based classification is given in [Table 1].
Ductal adenocarcinoma and its variants constitute about 90% of all cases. Non epithelial tumors are exceedingly rare. The rest of the entities are occasionally encountered with distinct clinical, radiological and histological features 1,2.
It is a form of blastomatous tumor with variable elements suggesting oncogenesis very early in embryonic life. This tumor usually occurs in children below 9 years 1. It is a slow growing tumor with late metastasis. Our case presented at the age of 32 years and showed metastasis in the lungs. Typically it is a large mass (7-17 cm) and may present with mass effect. Histologically it shows epithelial and mesenchymal elements, with frequent haemorrhagic necrosis. Prognosis is good if diagnosed before metastasis. On sonography, they are well-demarcated echogenic large masses with small hypoechoic areas. CT Scan depicts the tumor as in-homogeneous solid mass 1. MRI may show low to intermediate intensity signals in T1-weighted images and high intensity signals in T2 - weighted images 3.
Other Acinar Cell Tumors
Besides pancreatoblastoma, Acinar cell adenoma, Acinar cell carcinoma and Cystadenocarcinoma arise from acinar cells. Neoplasms of acinar cell orign are characterized by the immunocyto-chemical demonstration of pancreatic enzymes. They are negative for CEA and CA 19-9 6. Acinar cell carcinomas are usually found in elderly patients of both sexes. They are large, equally distributed, and frequently capsulated. They have soft consistency. Metastases are usually found in regional lymphnodes. Immunocyto-chemistry shows distinct staining pattern. Some patients present with metastatic fat necrosis in skin, bone or joint lesions with constitutional symptoms. Skeletal radiographs may reveal lytic lesions in both cancellous and cortical bones, usually beneath skin lesions and distal to knee and elbows. Prognosis is poor if liver metastasis occurs 4. Acinar cell cystadenocarcinoma is exceedingly rare. They are large and multiloculated. Metastasis occurs early. Zymogen granules on electron microscopy are suggestive of the diagnosis .
Serous Adenoma / Micro cystic Adenoma
It is a benign neoplasm most frequently observed in middle aged and elderly women. It may be an incidental finding or may present with abdominal pain/mass. They are slow growing tumors. Multiple constitutional and pathological abnormalities including diabetes mellitus have been reported. Rarely they can present with gastrointestinal hemorrhage or common bile duct obstruction. On cut-surface numerous cysts 1 to 20 mm in diameter with clear fluid are seen.
Plain radiographs show upper abdominal soft tissue mass with occasional calcification (centrally located, linear, arcuate or globular - sun-burst appearance). On sonography if cysts are less than 2 mm the mass may look homogeneous and solid. If larger cysts are present anechoic areas are seen. On CT Scan they are hypodense (10 - 40 HU), encapsulated and lobulated. With IV contrast the cysts and septae may be better seen. Selective angiography usually demonstrates highly vascular tumor with feeding arteries, tumor blush, neovascularisation and large draining veinis ,
Papillary cystic tumour
It is also described by other names - papillary tumor, papillary epithelial tumor and solid cystic tumor. Its histiogenesis is uncertain. Only about 174 cases have been reported in literature 10. It has been increasingly recognized in recent times. It may be detected incidentally or as a palpable mass in late stages. Tumor is more often located in the tail of pancreas.All our cases were seen in head of pancreas. Histologically uniform tumor cells are arranged either in solid sheets or papillae with fibrovascular cores projecting into the cystic spaces. Foci of cystic necrosis, hemorrhage or hyalinization are usually observed.
On sonography and CT Scan, tumors are seen as sharply defined, non-homogenous and large masses. Calcification is uncommon. CT Scan shows low-density areas of variable size corresponding to hemorrhage and necrosis. The cyst contents may have higher CT density than water. Masses with mixed content are hyperintense on T1 weighted images and hypointense on T2 weighted images. Angiography generally shows a mildly vascular mass on celiac injection ,,.
Mucinous cystic neoplasms
They are now regarded as benign, but potentially malignant. They usually occur in middle aged women and cause epigastric pain or an abdominal mass. Seventy to 90% occur in tail or body and rest in the head. Size of tumor varies from 1 to 20 cm. Those less than 3 cm are generally benign. In general they are slow growing with good prognosis. On cut surface uniloculated or multiloculated cyst filled with a thick mucinous or haemorrhagic fluid is seen. Unlike micro-cystic adenoma, these cysts are lined by tall mucin-producing columnar epithelium with goblet cells.
Plain radiographs show calcification in about 16% cases, which tend to arise in periphery of the tumor or in the walls of the cysts arranged in amorphous clumps. Gastro-intestinal barium series usually show extrinsic displacement. On sonography they are uni or multi-locular cystic masses with good through transmission and posterior wall enhancement. Demonstration of internal septae and visualization of nodular or papillary excrescenceses with irregular borders is most important for sonographic diagnosis. CT without contrast demonstrates a round to oval, well-encapsulated lesion with smooth external surface and attenuation value of near water density. Daughter cysts my be seen along the internal surface of large cysts. On IV contrast, the walls enhance and septae are clearer. On these findings alone mucinous cystadenoma and cystadeno carcinoma cannot be differentiated unless local invasion or metastasis is present in the later. On angiography they are hypervascular neoplasms with areas of lucency representing the cysts. ERCP may show displacement or encasement of pancreatic duct .
Ductectatic mucinous cystadenoma and cystadenocarcinoma (DCC):
In this newly recognized entity, the side branch of the main pancreatic duct is dilated. DCC tends to occur in older age and t here is no female predilection. It favors the uncinate process and head. CT Scan reveals cystic, slightly lobulated mass occurring in uncinate process or the head. Most of them are unilocular. Pancreatography is diagnostic which depicts dilatation of a side branch of the main pancreatic duct and looks like cluster of grapes due to contrast material. Filling defects of varying sizes within the lesion or in main pancreatic duct may laso be observed ,.
In recent literature the term "Intraductal papillary mucinous tumor of the pancreas (IPMT): has been introducted as a unifying label for the above two groups of mucin-producing neoplasms. IPMT are again classified as main-duct and branch-duct types. MR imaging and MR cholangio pancreatography are now considered superior to ERCP in these entities. Filling defects, diffuse main duct dilatation larger than 15 mm (main duct type) or segmental duct dilatation (branch duct type) have been suggested to indicate malignancy .
Subtypes of Ductal adenocarcinoma
Adeno-squamous cancer, micro-adenocarcinoma, anaplastic carcinoma, mucinous adenocarcinoma (colloid carcinoma) more or less mimic ductal adenocarcinoma, which can be differentiated only on histology .
Giant Cell (Pleomorphic) Carcinoma
It may be a highly malignant variant of ductal carcinoma. Some consider it as a sarcomatoid transformation of ductal carcinoma. They tend to be large with frequent hemorrhagic necrosis. Massive retroperitoneal adenopathy and haematogenic metastases are very common. Sonography and CT Scan depict it as a large thick walled cystic mass with ragged inner margin .
Osteoclast - Type Giant Cell Carcinoma
Only a few cases are reported. Prognosis is poor. Osteoclasts like giant cells within groups of mononuclear cells are seen. CT Scan and Sonography reveal multiple necrotic masses of pancreatic origin .
Other Rarer Tumors
Most metastases occur from melanoma, breast or lung carcinoma. Radiological findings mimic adenocarcinoma or lymphoma. If duct is obstructed features mimic those of pancreatitis (4,5). Pancreatic Lymphoma may occur more often in Histocytic lymphoma and Americna Burkitt's lymphoma. This turnor is characterized by large size, multifocality, associated widespread lymphadenopathy and one or more solid homogenous masses on CT Scan and very hypoechoic on sonography .
The ductal cell adenocarcinoma and its variants are the most common tumors involving pancreas. The role of radiological procedures in diagnosis and staging of these tumors is well defined.
The rarer tumors enumerated should be kept in mind as they have some distinct histology and radiological features. However, imaging modalities can give only a limited clue for diagnosis. CT guided FNAC can be of great diagnostic value. MR angiography and MR cholangiography are upcoming imaging modalities, which need further experience.
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