K-ras oncogene mutations indicate malignancy in cystic tumors of the pancreas

The incidence of intraductal papillary mucinous tumors of the pancreas(1)

To review a population-controlled single institution experience with intraductal papillary mucinous tumors (IPMTs) of the pancreas treated in the United States and generate an incidence of this recently described disease process.First decribed in 1982, mucin-secreting pancreatic cancer constituted a newly recognized category of pancreatic exocrine tumors distinct from mucinous cystic neoplasms. Since that time, several small series of IPMTs of the pancreas have been reported. Most studies come from Asia and Europe, with limited data from American institutions and no description of the incidence.The authors retrospectively reviewed all patients who underwent pancreatic resections at Madigan Army Medical Center from October 1992 through November 1999. Cases suggestive of IPMTs underwent re-examination by a staff pathologist. Clinical presentation, imaging studies, treatment, histopathology, and outcomes were reviewed for those with IPMTs. The data base of all patients eligible for care was evaluated to obtain a population denominator and determine an incidence for this neoplasm.Over 7 years, 78 patients underwent pancreatic resections. Forty-two had pancreatic neoplasms and, of those, 8 (19%) had IPMTs. The mean age was 67 years, with equal numbers of males and females. All patients were symptomatic (abdominal pain, 75%; jaundice, 25%; weight loss, 25%). Abnormal computed tomography scans were noted in 7/8 (88%) cases. Mucin was visualized during endoscopic retrograde cholangiopancreatography in 5/7 (71%) patients. Preoperative diagnosis of IPMT was made in 5 (62%) cases. The locations of the tumors were head (63%), tail (12%), head and body (12%), and body and tail (12%). All lesions were resectable, and procedures included 5 pancreatoduodenectomies, 2 distal pancreatectomies, and 1 total pancreatectomy. Main duct tumors were noted in 63%, whereas the remainder had both main and branch duct lesions. Tumor invasion was discovered in 2 (25%) cases. Mean follow-up was 29 months. Those without invasion were all alive (follow-up, 6 to 86 months). One patient with tumor invasion died 4 months after surgery and the other was living 20 months later. The incidence of IPMTs was 1 case/281,000 patients/year.The incidence of IPMTs of the pancreas may be higher than previously recognized. Aggressive resection is warranted based on the favorable prognosis of patients without tumor invasion.

Pathologic examination accurately predicts prognosis in mucinous cystic neoplasms of the pancreas

The behavior of pancreatic mucinous cystic neoplasms has long been debated. Some authors contend that histologically benign neoplasms can recur and metastasize. We reviewed the gross and microscopic findings and outcomes of 61 mucinous cystic neoplasms diagnosed at The Johns Hopkins Hospital from March 20, 1984 to July 8, 1998. Each neoplasm was placed into one of four categories based on complete histologic examination: invasive mucinous cystadenocarcinoma, mucinous cystic neoplasm with in situ carcinoma, borderline mucinous cystic neoplasm, and mucinous cystadenoma. Neoplasms in the latter three categories were included only if they were entirely resected and completely examined. Patient outcomes were obtained from hospital records and patient and physician follow-up. Twenty (33%) of the patients had invasive mucinous cystadenocarcinomas, and they had 2- and 5-year disease-specific survival rates of 67% and 33% (mean follow-up of survivors, 4.2 years), respectively. Nine (15%) patients had mucinous cystic neoplasms with in situ carcinoma (mean follow-up of survivors, 4.1 years). Five (8.2%) patients had borderline mucinous cystic neoplasms (mean follow-up of survivors, 5.6 years). Twenty-seven (44%) patients had mucinous cystadenomas (mean follow-up of survivors, 5.1 years). No mucinous cystadenoma, borderline mucinous cystic neoplasm, or mucinous cystic neoplasm with in situ carcinoma recurred or metastasized. No patient with the diagnosis of mucinous cystadenoma, borderline mucinous cystic neoplasm, or mucinous cystic neoplasm with in situ carcinoma died of disease. The difference in disease-specific survival rates between patients with invasive mucinous cystadenocarcinomas and those with noninvasive tumors was significant (p < 0.0001, log-rank test). One case, originally showing only benign histology on incisional biopsy, contained foci of invasive carcinoma on complete resection. Completely resected and entirely examined mucinous cystadenomas, borderline mucinous cystic neoplasms, and mucinous cystic neoplasms with in situ carcinoma follow benign courses. Because invasive carcinoma can be focal, failure to study an entire mucinous cystic neoplasm may result in the miscategorization of a malignant neoplasm as benign.

Sequential accumulation of K-ras mutations and p53 overexpression in the progression of pancreatic mucinous cystic neoplasms to malignancy

OBJECTIVE

Pancreatic mucinous cystic neoplasms (MCNs) provide a spectrum of neoplastic changes ranging from benign to malignant. The authors have correlated K-ras mutations and p53 overexpression with the evolution of these tumors.

METHODS

Areas of mild, moderate, or severe dysplasia were microdissected from paraffin-embedded tissue sections of 28 different MCNs (10 benign, 9 borderline, 9 malignant). Nonneoplastic pancreatic ducts were also microdissected from tissues adjacent to the tumors. Ten serous cystadenomas served as negative controls. K-ras codon 12 mutations were identified by a mutant-enriched nested polymerase chain reaction-restriction fragment length polymorphism assay and confirmed by sequencing. p53 overexpression was demonstrated by immunohistochemistry.

RESULTS

K-ras mutations were detected in 20% of benign, 33% of borderline, and 89% of malignant MCNs. Histologically, mutations were found in 26% (7/27) of MCN epithelia with mild dysplasia, 38% (5/13) of MCN epithelia with moderate dysplasia, and 89% (8/9) of MCN epithelia with severe dysplasia or carcinoma. Ten percent (4/39) of nonneoplastic pancreatic ducts at the margins of MCN harbored mutations, all associated with borderline or malignant tumors. Overexpression of p53 occurred in none of the benign or borderline MCNs but in 44% (4/9) of the malignant tumors (p = 0.006 benign/borderline vs. malignant). p53 immunoreactivity was concentrated in areas of severe dysplasia/carcinoma or invasion, where K-ras mutation had been detected.

CONCLUSION

These findings demonstrate a sequential accumulation of genetic changes in the carcinogenesis of MCN. K-ras mutations appear early and increase in proportion with increasing dysplasia. Overexpression of p53 is a late finding observed only in carcinomas, and in combination with mutated K-ras genes. The presence of K-ras mutations in nonneoplastic ducts supports formal pancreatic resection over enucleation for treatment. Mucinous cystic neoplasms may be a useful model to study the evolution of pancreatic ductal adenocarcinomas, in which precursor lesions remain unknown.

Cystic pancreatic neoplasms

Cystic pancreatic neoplasms comprise a heterogeneous group of pathologic entities. Mucinous cystic tumors and serous cystadenomas account for more than 75% of reported cases. While serous cystadenomas are almost uniformly benign, mucinous cystic tumors all have malignant potential and must be treated as such. While both clinical and biochemical features can distinguish among the various cystic pancreatic lesions, surgical resection is often required for both definitive diagnosis and treatment. When surgery is performed, benign lesions should be treated with pancreatic parenchymal sparing procedures if anatomy permits. Standard surgical oncologic principles should be employed when treating indeterminate or malignant lesions.

Molecular genetics and related developments in pancreatic cancer

Cancer of the pancreas is a genetic disease. The most common genetic alterations identified to date in pancreatic cancer are activation of the K-ras oncogene (approximately 90%) and inactivation of the p16 (approximately 95%), p53 (50% to 75%), DPC4 (55%), and BRCA2 (7%) tumor suppressor genes. An understanding of the molecular genetics of carcinoma of the pancreas is important because it may help explain the aggregation of pancreatic cancer in families and may lead to the development of novel tests to detect early cancers. For example, the aggregation of pancreatic cancer in some families has been shown to result from inherited mutations in cancer-causing genes, and genetic alterations shed from pancreatic cancers have been detected in stool specimens. In addition, we believe that an improved knowledge of the molecular genetics of pancreatic cancer will lead to the development of a new generation of rational and more effective treatments.

Cystadenomas and cystadenocarcinomas of the pancreas: a multiinstitutional retrospective study of 398 cases. French Surgical Association

OBJECTIVE

To review the features of patients with benign and malignant cystadenomas of the pancreas, focusing on preoperative diagnostic accuracy and long-term outcome, especially for nonoperated serous cystadenomas and resected cystadenocarcinomas.

SUMMARY BACKGROUND DATA

Serous cystadenomas (SCAs) are benign tumors. Mucinous cystic neoplasms should be resected because of the risk of malignant progression. A correct preoperative diagnosis of tumor type is based on morphologic criteria. Despite the high quality of recent imaging procedures, the diagnosis frequently remains uncertain. Invasive investigations such as endosonography and diagnostic aspiration of cystic fluid may be helpful, but their assessment is limited to small series. The management of typical SCA may require resection or observation. Survival after pancreatic resection seems better for cystadenocarcinomas (MCACs) than for ductal adenocarcinomas of the pancreas.

METHODS

Three hundred ninety-eight cases of cystadenomas of the pancreas were collected between 1984 and 1996 in 73 institutions of the French Surgical Association. Clinical presentation, radiologic evaluation, and surgical procedures were analyzed for 144 operated SCAs, 150 mucinous cystadenomas (MCAs), and 78 MCACs. The outcome of 372 operated patients and 26 nonoperated patients with SCA was analyzed.

RESULTS

Cystadenomas represented 76% of all primary pancreatic cystic tumors (398/522). An asymptomatic tumor was discovered in 32% of patients with SCA, 26% of those with MCA, and 13% of those with MCAC. The tumor was located in the head or uncinate process of the pancreas in 38% of those with SCA, 27% of those with MCA, and 49% of those with MCAC. A communication between the cyst and pancreatic duct was discovered in 0.6% of those with SCA, 6% of those with MCA, and 10% of those with MCAC. The main investigations were ultrasonography and computed tomography (94% for SCA, MCA, and MCAC), endosonography (34%, 28%, and 22% for SCA, MCA, and MCAC respectively), endoscopic retrograde cholangiopancreatography (16%, 14%, 22%), and cyst fluid analysis (22%, 31%, 35%). An accurate preoperative diagnosis of tumor type was proposed for 20% of those with SCA (144 cases), 30% of those with MCA, and 29% of those with MCAC. An atypical unilocular macrocyst was observed in 10% of SCA cases. The most common misdiagnosis for mucinous cystic tumors was pseudocyst (9% of MCAs, 15% of MCACs). Intraoperative frozen sections (126 cases) allowed a diagnosis according to definitive histologic examination in 50% of those with SCA and MCA and 62% of those with MCAC. For management, 93% of patients underwent surgery. Nonoperated patients (7%) had exclusively typical SCA. A complete cyst excision was performed in 94% of benign cystadenomas, with an operative mortality rate of 2% for SCA and 1.4% for MCA. Resection was possible in 74% of cases of MCAC. Mean follow-up of 26 patients with nonresected SCAs was 38 months, and no patients required surgery. For resected MCACs, the actuarial 5-year survival rate was 63%.

CONCLUSIONS

Spiral computed tomography is the examination of choice for a correct prediction of tumor type. Endosonography may be useful to detect the morphologic criteria of small tumors. Diagnostic aspiration of the cyst allows differentiation of the macrocystic form of SCA (10% of cases) and the unilocular type of mucinous cystic neoplasm from a pseudocyst. Surgical resection should be performed for symptomatic SCAs, all mucinous cystic neoplasms, and cystic tumors that are not clearly defined. Conservative management is wholly justified for a well-documented SCA with no symptoms. An extensive resection is warranted for MCAC because the 5-year survival rate may exceed 60%.

[Cystic lesions of the pancreas]

Most cystic lesions of the pancreas are pseudocysts caused by acute or chronic pancreatitis. Congenital cysts are rare and may occur in congenital syndromes like von Hippel-Lindau syndrome. Cystic tumors of the pancreas may be difficult to distinguish clinically; however, because of their malignant potential, in particular in cases of mucinous types, diagnostic verification is crucial. Hence, in all cases of cystic lesions of the pancreas, which are not a sequela of an etiological confirmed acute or chronic pancreatitis, a cystic neoplasm must be ruled out. Differential diagnosis may be difficult even with ultrasonography, computertomography, endoscopic retrograde cholangiopancreatography and serum analyses; endoscopic ultrasound, magnetic resonance tomography and analysis of the cyst content may be of particular value. The therapeutic approach for pseudocysts is now well established and guided by symptoms and complications. If a cystic neoplasm is suspected, surgical resection of the complete lesion is warranted.

CONCLUSION

The most important differential diagnosis in all cystic lesions of the pancreas with atypical presentation includes a cystic neoplasm. Therefore complete resection is indicated whenever the suspicion cannot be ruled out.

Genomic anomalies in pancreatic tumors other than common adenocarcinoma

In recent years enormous advances have been made in the understanding of the molecular mechanisms governing pancreatic ductal adenocarcinoma. However, little is known about other pancreatic neoplasms, which include intraductal papillary mucinous (IPMT), serous cystic (SCT), mucinous cystic (MCT), solid pseudopapillary (SPT), acinar and islet cell tumors. In addition, the study of tumors grouped under the unfortunate term of periampullary cancers will help distinguish the pathogenetic features of these neoplasms, often confused with pancreatic head neoplasms. The available data suggest that the less common pancreatic tumor types do not generally follow the same molecular pathway as the more common ductal carcinoma. IPMT seems to contain chromosomal anomalies similar to those found in ductal cancers, whereas papilla of Vater and duodenal cancers show genetic anomalies resembling those of gastrointestinal malignancies. The application of genome-wide screening techniques to these less common pancreatic tumors will undoubtedly play a central role in unraveling the complexity behind their pathology.

Malignant fibrous histiocytoma of the pancreas: a case report with genetic analysis

BACKGROUND

Malignant fibrous histiocytoma (MFH) is the most common type of soft tissue sarcoma in adults; it occurs frequently in the extremities, the trunk, or retroperitoneal tissues. MFH rarely is detected in digestive organs, such as the liver or stomach.

METHODS

The authors report a patient with MFH of the pancreas who was treated with surgery alone. The tumor was studied for genetic alterations in the p53, p16ink4a, and DPC4 tumor suppressor genes as well as the K-ras oncogene by immunohistochemistry, single strand conformation variant (SSCV) analysis, and direct DNA sequencing.

RESULTS

The authors believe that this is the 13th report of primary pancreatic MFH in the world literature and the first genetic analysis of this rare tumor. The patient is alive with no evidence of recurrence 34 months after surgery. Immunohistochemistry revealed no abnormal accumulation of the p53 protein and normal nuclear p16 expression. Mutation analysis of the p53, p16, DPC4, and K-ras genes showed only a polymorphism at codon 72 of the p53 gene and no mutations in any of the genes.

CONCLUSIONS

Genotypically, MFH of the pancreas is clearly different from other malignant pancreatic tumors, which further supports the hypothesis that this tumor is a rare but distinct entity.