Pancreatic carcinoma

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Introduction :
Carcinoma of the pancreas is a highly malignant tumor with poor prognosis (The overall 5-year survival rate for this disease is less than 5%). It represents 95% of all malignant pancreatic tumors. 60% are round in the head of the pancreas, 20 per cent in the body or rail of the pancreas and 20 pet cent involve the whole pancreas. About 80% of tumors in the pancreas are focal. It primarily occurs in the sixth to eighth decades of life with a male preponderance. The risk factors include alcohol abuse, diabetes, smoking , asbestos exposure, hereditary pancreatitis and chronic calcific pancreatitis. Histologically 95 pet cent of pancreatic carcinomes are adenocarcinoma, which usually originale from ductal elements.

Pathophysiology:
Pancreatic cancers can arise from both the exocrine and endocrine portions of the pancreas. Of pancreatic tumors, 95% develop from the exocrine portion of the pancreas, including the ductal epithelium, acinar cells, connective tissue, and lymphatic tissue.
Typically, pancreatic cancer first metastasizes to regional lymph nodes, then to the liver, and less commonly, to the lungs. It can also directly invade surrounding visceral organs such as the duodenum, stomach, and colon.

Clinical :
weight loss, abdominal pain, back pain, anorexia, nausea and vomiting, generalized malaise and weakness.

Ultrasound :
The detection rate by any imaging procedure depends on an adequately visualized gland. The tumors in the head present earlier than the others, usually because they cause obstruction to the biliary tract. Common bile duct dilatation occurs in 80 to 90 pet cent of pancreatic head carcinomes, with small carcinomes common bile duct dilatation may be the only ultrasound abnormality.
The ultrasonic findings include a focal mass which is generally less echogenic than the normal gland. Pancreatic carcinoma is often well defined with irregular margins. Its echogenicity varies depending on the size and presence of necrosis and/or local bleeding. The most important is a localized change in the echogenicity of the pancreas, usually focal and hypoechoic. 95% were hyperechoic (similar to this case). In addition, the borders of the mass are irregular, and the mass is usually quite distinct from the rest of the gland. Early small tumors are homogeneous and hypoechoic. Larger tumors (>5cm in size) with hemorrhagic or necrotic changes are nonhomogeneous and vary in echogenicity. The rest of the pancreas may be normal or abnormal depending on the associated pancreatitis due to ductal obstruction. Thickening of tissues around the coeliac axis or mesenteric vessels may be due to invasion of the lymphatics.
The pancreatic duct may also be dilated. Obstruction of the common bile duct can be produced by the direct effect of the mass in the pancreatic head or adenopathy. In some cases, ductal dilatation is the only sign of carcinoma.
Other associated findings in carcinoma include dilated pancreatic duct (18%), dilated central and peripheral bile ducts, nodal metastasis, liver metastasis, compression or tumor invasion involving portal vein or its major tributaries, mesenteric vessel, inferior vena cava, and splenic vein displacement; and ascites. Abrupt obstruction with acute dilation of pancreatic duct proximal to obstruction is strongly suggestive of carcinoma. Vascular displacement is more common with tumors in the body and tail of pancreas.
Lymphatic spread is to the celiac, superior mesenteric, paracaval, retrocaval and porta hepatis nodes. Vascular invasion is to the liver, lungs and peritoneal cavity. Venons thromboses may occur especially with the body or rail tumours. Less frcquently direct invasion of duodenum, stomach, colon, gallbladder, adrenal gland and kidney may occur.
Endoscopic ultrasonography (EUS): EUS obviates the physical limitations of TUS by placing a high-frequency ultrasonographic transducer on an endoscope, which is then positioned in the stomach or duodenum endoscopically to help visualize the head, body, and tail of the pancreas. In numerous series, EUS has detection rates of 99-100% for all pancreatic carcinomas, including those smaller than 3 cm. EUS is as accurate as other methods for assessing the etiology of obstructive jaundice. An additional significant diagnostic advantage is EUS-guided fine-needle aspiration, which allows for the simultaneous cytologic confirmation of pancreatic carcinoma at the time of EUS diagnosis. EUS appears to be equivalent to dual-phase spiral CT scanning for assessing tumor resectability potential.
Fine-needle percutaneous biopsy of abdominal mass lesions is a safe and effective other method to obtain tissue samples for cytologic and histologic analysis.

Differential :
The differential diagnosis of pancreatic masses is difficult because chronic pancreatitis (particularly if the pathological changes are focal) and pancreatic cancer show similar clinical and imaging patterns, and the possibility of metastases, lymphoma, leukemia, and myeloma, should be considered.
The presence of calcification or intraductal calculi makes chronic partcreatitis more likely but does not exclude a carcinome.
Masses adjacent to the pancreas may be mistaken for pancreatic masses: retroperitoneal varices, retroperitoneal masses, lymphatic masses or nodes, renal tumours, arterial aneur-ysms. Marked dilatation of the pancreatic duct alone does not necessarily indicate malignant disease. Severe dilatation can result from malignant obstruction of the pancreatic duct or chronic pancreatitis. Idiopathic fibrosis within the pancreatic head can also cause marked biliary and pancreatic ductal dilatation. Dilatation can also be seen with carcinoma of the ampulla, cholangiocarcinoma near the ampulla, Crohn's disease of the duodenum, and stenosis of the ampulla.

Treatment :
The only therapy that has definitively been shown to increase the survival of patients with pancreatic cancer is surgical resection : pancreaticoduodenectomy (Whipple operation). Some institutions use neoadjuvant chemotherapy and radiation therapy to try to improve the resectability potential of locally advanced cancers.

References
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