Hypodense lesion pancreatic tail with distal ductal dilatation and atrephy distel to the lasion.
DUCT CELL ADENOCARCINOMA AND VARIANTS:
Duct Cell Adenocarcinoma and variants account for the vast majority of all pancreatic neoplasms. There are approximately 24,000 new cases seen and 20,000 deaths annually reflecting the extremely poor prognosis associated with this malignancy. The prevalence of the disease is approximately 10 per 100,000 but increases to 100 per 100,000 by the age of 75. The only established risk factor is smoking with a relative risk of 1.5.
The histology of ductal adenocarcinoma varies from well to poorly differentiated forms based upon the degree of cellular atypia of the epithelium and the degree to which the cancerous elements attempt to form duct-like structures, Variants of ductal adenocarcinoma are rare and most portend an even worse prognosis than the typical form of ductal adenocarcinoma. One variant, pleomorphic giant cell carcinoma is worth mentioning as it may resemble a low grade malignancy, a solid and papillary epithelial neoplasm
The initial signs and symptoms of the disease are often vague and non-specific including diffuse abdominal pain (possibly due to the tumor's proclivity for perineural spread) weight loss, depression, fatigue, nausea and vomiting. Frequently, the pain experienced by the patient radiates to the back. Jaundice is the presenting sign in fifty percent of patient's with pancreatic head tumors. Evidence of metastatic disease is common at presentation. The best prognosis is seen in the rare patient with an obstructing lesion in the head of the pancreas, near the common bile duct resulting in jaundice and leading to an earlier evaluation. Diabetes occurs in twenty five to fifty percent of patients with pancreatic carcinoma, presumably secondary to pancreatic duct obstruction and atrophy of the proximal gland. Alternatively, pancreatic duct obstruction may result in pancreatitis.
Computed tomography is clearly the superior modality for imaging the pancreas. The pancreas is imaged at 5 mm intervals following the administration of intravenous and enteric contrast. Ultrasound images may be hampered by the presence of overlying bowel gas. MRI is costly. Angiography is not useful for screening, but may be useful in selected patients. CT not only images the pancreas well, but is advantageous in evaluation of the peripancreatic tissues for adenopathy, degree of local spread of disease and for associated inflammatory changes.
Unfortunately, despite good technique, the detection of pancreatic adenocarcinoma often relies solely upon a change in contour of the gland since the majority of lesions are typically isodense with the parenchyma. The majority of malignancies are not detected until the mass is 2-3 cm in size, at which time the tumor is usually non-resectable. The reported upper limit of normal measurements are the following: 3 cm for the pancreatic head and 2.2 cm for the body. Measurements of the pancreatic tail are not as reliable since the tail may normally be bulbous. The majority of pancreatic carcinomas arise within the head. Approximately 20% arise within the body and tail or are diffuse in nature. A decreased zone of central attenuation may be seen due to the hypovascular, scirrous nature of the tumor. A common finding, as previously mentioned, is enlargement of the pancreatic duct proximal to the point of obstruction with associated gland atrophy and possible obstruction of the common bile duct if the mass is within the pancreatic head.
Beyond simply recognizing that a pancreatic mass is present by detecting a change in gland contour, enlargement of the CBD and/or pancreatic duct, and atrophy of the gland, the role of the radiologist is to help determine whether or not the patient's malignancy is resectable. It is also important to identify anomalous vessels such as a replaced right hepatic artery prior to surgery. Evidence of metastatic disease (most commonly to the liver or lungs) and signs of vascular invasion ( most commonly of the SMA, SMV or portal confluence) preclude resectability. The most reliable sign of vascular invasion is loss of the normal fat plane between the gland and the superior mesenteric vessels. Angiography may also be a useful additional test. Between 85 to 95% of patients are considered inoperable at the time of diagnosis base on the above criteria.
After a patient has been determined to be resectable using CT criteria, studies have shown that it is prudent to perform laparoscopy as small, 1-2mm peritoneal and omental metastases are found in up to 40% of patients which deems the patient inoperable.
Patients who are deemed inoperable my undergo fine needle aspiration (FNA) under CT guidance to exclude the presence of unusual disease processes mimicking the presence of pancreatic carcinoma such as sarcoid, tuberculosis or another less lethal malignancy. The sensitivity of FNA is believed to be 60 to 95%.
The prognosis of patients with pancreatic adenocarcinoma is decidedly grim. Of 60 cancer sites reported by the annual cancer statistics review, the 3 percent five year survival rate for patients with pancreatic adenocarcinoma is the worst. The only known cure is a Whipple's procedure. This procedure includes pancreaticoduodenectomy, end to end reanastomosis of the pancreatic tail with the distal duodenum, choledochojejunostomy, partial gastrectomy, gastrojejunostomy and vagotomy. The biliary and pancreatic anastomoses are at the afferent loop to reduce the incidence of marginal ulcers at the gastrojejunostomy site. For this reason, the vagotomy is also performed. In experienced hands, the Whipple's procedure carries an associated 5% mortality and a five year survival rate of 17%. There have only been approximately 200 "cures" due to resection in the literature. Generally only pancreatic head masses are resectable since virtually all tail masses present beyond the stage of resectability.
In most patients palliation is key as resectability is not an option. Relief of jaundice may be obtained with biliary enteric bypass and relief of obstruction from gastrojejunostomy. More commonly, relief of jaundice may now be obtained with percutaneously or endoscopically placed stents. In patients with intractable pain, a celiac nerve block may be performed. Sympathetic nerves within the celiac plexus carry pain fibers from the pancreas. Therefore, pain can be controlled with chemical extirpation between the level of the celiac and SMA arteries. Lidocaine and Epinephrine are first injected along with contrast under CT guidance. The approach may be anterior, paracrural or transaortic. After confirming correct location with CT localization and documenting pain relief, pure Ethyl alcohol is injected in the region of the celiac plexus. The potential benefit is relief of pain, but potential risks include but are not limited to new pain and paralysis.