Nonfunctioning islet cell tumors of the pancreas: a difficult diagnosis but one worth the effort.

Islet cell tumors of the pancreas usually secrete gastroenteropancreatic peptides causing well-recognized clinical syndromes. Description of these syndromes and the identification of the responsible hormones by radioimmunoassay has led to a better understanding of neuroendocrine regulatory function. More recently, similar tumors have been seen that contain various peptides on immunohistochemical stain but do not secrete these substances sufficiently to cause clinical symptoms. Nonetheless, they have the same malignancy and metastatic rate as most of the functional tumors. Between 1972 and 1996, 44 patients with islet cell tumors have been treated at the Indiana University Medical Center Hospital, and of these 14 have been nonfunctional. Preoperative imaging studies, such as CT scan and endoscopic ultrasound, were able to visualize a lesion but not to make the specific diagnosis, even with fine-needle aspiration. Pancreatic ductal preservation on endoscopic retrograde cholangiopancreatography with CT evidence of a mass should arouse suspicion of an islet cell tumor. Once discovered, all but 1 of the 14 patients has under gone resective therapy, with only 1 postoperative death. Treatment has been aggressive, with 11 of the 13 resected patients undergoing pancreaticoduodenectomy, and 2 others distal pancreatectomy. Four of the seven patients with positive lymph node metastases are dead, while all patients with negative nodes are still alive. Thus far, 10 of the original 14 patients are alive, surviving an average of 32.7 months, with a median survival of 31.1 months. Because these tumors have a better overall prognosis, vigorous attempts at total or subtotal resection should be carried out, since the long-term survival is enhanced by tumor bulk reduction or curative resection when possible.