Colloid (mucinous noncystic) carcinoma of the pancreas

In the past, colloid (mucinous noncystic) carcinoma (CC) of the pancreas ha d been included under the category of ordinary ductal adenocarcinoma, a tum or with a dismal prognosis, or was frequently misdiagnosed as mucinous cyst adenocarcinoma. The clinicopathologic features of CC have not vet been well characterized, because most cases on record have been parts of studies on either mucinous cystic neoplasms (MCN) or intraductal papillary mucinous ne oplasms (IPMN), with which colloid carcinomas are frequently associated. To determine the clinicopathologic characteristics of CC, 17 pancreatic tumor s composed predominantly (>80%) of CC (defined as nodular extracellular muc in lakes with scanty malignant epithelial cells) and in which the invasive carcinoma measured larger than 1 cm were studied. Ten of these were origina lly classified as mucinous ductal adenocarcinoma and four as mucinous cysta denocarcinoma. The mean age of the patients was 61 years; 9 were men and 8 were women. The mean size of the CC was 5.3 cm (range, 1.2-16 cm). In more than half of the patients, CC represented the invasive component of an IPMN (in nine cases) or MCN (in one case). The tumors were composed of well-def ined pools of mucin with sparse malignant cells in various patterns of dist ribution. Signer-ring cells floating in the mucin (but not as individual ce lls infiltrating stroma, a characteristic finding of signet-ring cell adeno carcinomas) were commonly identified and were prominent in five cases. Peri neurial invasion was noted in six cases and regional lymph node metastases in eight. Mutation in codon 12 of the k-ras gene was detected in only 4 of 12 cases studied and p53 mutation in 2 of 9. Immunohistochemical and histoc hemical mucin stains suggested luminalization of the basal aspects of the c ells. Five-year survival was 57%. At an overall mean follow up of 57 months , 10 patients were alive with no evidence of disease (median, 79 mos), incl uding four with lymph node metastasis. three others with perineurial invasi on, and another with vascular invasion. Four patients died of disease (18, 18, 25, and 26 mos), and three died of thromboembolism (with persistent dis ease) at 2, 5, 10 months. All seven patients who died with or of tumor had undergone incisional biopsy of the turner either before the operation or in traoperatively, whereas none of the patients who were alive had incisional biopsy. When compared with 82 cases of resectable ordinary ductal adenocarc inoma on whom followup and staging information was complete, it was found t hat the patients with CC present with larger tumors (p = 0.03) but lower st age (p = 0.01). The prognosis of CC is significantly better: 2-year and 5-y ear survival are 70% versus 28% and 57% versus 12%, respectively (p = 0.001 ). In conclusion, pancreatic CC may occur with or without an identifiable I PMN and MCN component, and should be distinguished from mucinous cystadenoc arcinoma, ordinary ductal adenocarcinoma, and signet-ring cell adenocarcino ma. CC of the pancreas is associated with a significantly better prognosis than ordinary ductal adenocarcinoma. In addition to its distinctive morphol ogic and clinical characteristics, CC of the pancreas also appears to have a low incidence of mutation in codon 12 of the k-ras gene. In cases with a clinical suspicion of colloid carcinoma, the possibility that an incisional biopsy may contribute to thromboembolic complications or even disseminatio n of the tumor may need to be considered. The luminalization of the basal a spects of the tumor cells may be the cause of stromal mucin accumulation th at characterizes colloid carcinoma and may oct as a containing factor.