Pancreatic neuroendocrine tumors: insulinoma
What are the treatment options for insulinoma, both the benign and the malignant?
Standard Open Surgical Approach. Because the pancreas extends across the back of the upper abdomen, a reasonably large incision is used to allow access with looking at and feeling the entire pancreas. Even with preoperative imaging, the insulinoma may still be difficult to locate, as they are usually buried within the substance of the pancreas tissue and not visible on the surface of the pancreas. With surgical manipulations, the pancreas can be felt with thumb and fingers on front and back of the pancreas, allowing the usually more firm insulinoma to be felt. IOUS is utilized at this point to find or confirm the location of the tumor and the important anatomic structures, most importantly the main pancreatic duct. Rarely, more than 1 insulinoma may be encountered, even in sporadic cases. The 2 choices for the method of surgical removal of the insulinoma are enucleation or pancreatic resection
Enucleation. The consistency of the insulinoma is usually a very compact ball of cells, usually more firm than the surrounding pancreas tissue. The interface between the insulinoma and pancreas tissue is usually clearly visible, and can be dissected cleanly by the surgeon, assuring that the entire tumor is removed. Sometimes, even when the tumor sits against the main pancreatic duct, the 2 can be separated without injury to the duct (Figure 1). However, if the tumor is large, or if the relationship between the duct and the tumor is difficult, then duct injury can be a major risk. In such a situation, it may be preferable to remove some normal pancreas with the insulinoma within it, and manage the pancreatic duct separately.
A. Intraoperative picture of typical reddish insulinoma in the body of the pancreas, unusually visible on the surface of the pancreas.
|B. The tumor has been nearly enucleated|
|C. After the tumor has been removed, the pancreatic duct (white structure pointed to by yellow arrow) is visible which was behind the tumor.|
Pancreatic Resection. The location of the tumor within different regions of the pancreas may influence the conduct of the operation considerably. The head of the pancreas is so inter-attached to many other anatomic structures, that resection (Whipple procedure) carries a very significant chance of complications (40% at least) even if the tumor is successfully removed. In contrast, the tail of the pancreas, while close to the spleen, can be removed much more safely (either with or without removing the spleen).
Laparoscopic Resection of Insulinoma. As with many operations a more minimally invasive approach has been pioneered for removal of insulinomas. The safest zones for this approach are the body and tail of the pancreas. Sometimes enucleation, but often limited distal pancreatectomy can be accomplished laparoscopically by highly skilled minimally invasive surgeons. This usually requires confident preoperative localization, use of laparoscopic intraoperative ultrasound, and special dissection techniques. The management of the pancreatic duct remains the largest source of postoperative complications with this method, occurring in up to 30-40% of patients.
Surgical Complications. These may occur in up to 40-50% of patients, but many are minor, often minimally affecting length of hospitalization, and few require reoperation. The drainage of the main pancreatic duct is "downhill" toward the head and into the duodenum. Removing portions of the left side of the pancreas (nearer the spleen, called distal pancreatectomy) necessitates successful closure and sealing of the main pancreatic duct and the small tributaries (like small branches and twigs off the trunk of a tree). But even if a small leak occurs from the distal pancreatic duct, it generally seals within a few days to weeks of the operation without need for reoperation. A drain may be necessary temporarily. The spectrum of pancreatic complications include bleeding, abscesscollection of pus, pancreatitisinflammation of the pancreas, pseudocyst or fistulacollection of pancreatic juice in the abdomen, or drainage of that fluid out through an opening in the abdominal walloften collected in a drain. These are the most frequent problems encountered, and all can usually be managed without need for reoperation. Infections in the incision or urine, blood clots in the legs, and lung problems are the most frequent non-pancreatic problems. In many institutional reports, no patients have died from these operations.
Figure 2: Malignant insulinoma, removed with a Whipple procedure (portion of stomach, entire duodenum, portion of bile duct, head of the pancreas including the insulinoma cancer are removed, remaining normal structures put back together). Note the white, irregular cancer in contrast to the small benign insulinomas pictured above.
Malignant Disease. Insulinomas are malignant in less than 10% of patients. The prognosis for patients with malignant insulinoma is far better than for patients with the more common exocrine pancreatic cancer. Not only does the tumor secrete insulin, so do any sites of spread of the cancer. An aggressive surgical approach to the tumor and the metastases (spread of cancer in other parts of the body; with insulinoma typically to the liver and lymph nodes) is usually recommended (Figure 2). Chemotherapy and other specialized forms of treatment may be necessary for these patients.