Pancreatic endocrine tumour with ductules: further observations of an unusual histological subtype

AIMS

Pancreatic endocrine tumours (PET) containing ductules are an uncommon histological variant. Considerable conjecture surrounds the origin and histogenesis of the ductules. Opinions range from the ductules being an inherent part of the tumour, to others who feel they are merely entrapped. A study of 21 cases of this variant was undertaken with particular attention paid to the distribution and morphology of the ductules, the presence of entrapped acinar tissue and the surrounding uninvolved pancreatic tissue.

METHODS AND RESULTS

Twenty-one cases were detailed occurring in either gender equally and with a wide age range (19-85 years). All cases, except one, were sporadic, the vast majority were located in the tail and were of small size (less than 2.0 cm). All cases were typified by stromal fibrosis, either diffuse (15) or in the form of septae (6). Embedded within the fibrous tissue were ductular structures, some of which were dilated and ectatic. The ductules were centrally located (5), at the periphery of the tumour (9) or diffusely scattered throughout the lesion (7). All cases showed ductulo-insular complexes. Insulin was demonstrated in 15 immunohistochemically.

CONCLUSIONS

It is likely that in some cases the ductules are entrapped as the tumour grows into surrounding normal pancreatic tissue and the ductular proliferation is a secondary phenomenon. In a proportion of cases, the ductules are likely to be a part of the tumour arising as part of focal chronic inflammation or as a result of the growth factor effects of insulin, in cases associated with insulin production. There is nothing to suggest that the ductules confer any special biological characteristics to the PET and are merely a histological nuance. However, some cases may have a dominant tubular component, which could present problems at frozen section where the association with fibrosis may invoke a mistaken diagnosis of pancreatic ductal adenocarcinoma or chronic pancreatitis.

Multihormonality and entrapment of islets in pancreatic endocrine tumors

We analyzed pancreatic endocrine tumors (PETs) from 200 patients for the incidence of multihormonality and entrapped islets and correlated the results with clinicopathological features. Our series included 86 cases (43%) of functioning PET and 114 cases (57%) of nonfunctioning PET. Classified according to the WHO classification, there were 32 well-differentiated benign PETs, 85 well-differentiated PETs with uncertain behavior, and 83 well-differentiated malignant PETs. All tumors were immunostained for pancreatic hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) and for additional hormones such as gastrin, vasoactive intestinal polypeptide, calcitonin, seratonin, and adrenocorticotropic hormone. Multihormonality was found in 34% of all PETs and it was a frequent finding in the tumors of the uncertain behavior (38.8%) group. Islet entrapment was found in 57 tumors (28.5%) and was significantly more frequent in PETs with uncertain and malignant behavior than benign ones (p=0.01). In 57 cases, we also investigated whether ductule entrapment accompanied islet entrapment. Of these 57 tumors, 45 (79%) tumors had accompanying ductule entrapment. Ductule entrapment did not show significant correlation with malignancy and was a more frequent finding in nonfunctioning tumors. We conclude that the incidence of multihormonality in PETs is not as high as suggested previously and islet entrapping may reflect aggressive tumor growth and may be a complementary criterion for predicting the biological behavior of PETs.

Differences in survival for patients with resectable versus unresectable metastases from pancreatic islet cell cancer

Well-differentiated islet cell tumors can be associated with aggressive biology, resulting in early metastases to the liver. This study was carried out to determine whether survival for patients with malignant islet cell tumors and synchronous liver metastases is affected by complete surgical resection. Thirty-one patients with synchronous liver metastases from islet cell cancer underwent surgical exploration with the intent for complete tumor resection, and all patients underwent resection of the pancreatic primary. The patients were divided into two groups, those with resectable versus unresectable liver metastases. Twenty-six of 31 (84%) patients underwent complete resection of both the primary tumor and all liver metastases, and 5 (16%) patients underwent only complete resection of the pancreatic primary without liver resection. To extirpate the primary tumor, a pancreaticoduodenectomy was performed in 11 of the 26 (42%) completely resected patients and in 4 of the 5 (80%) incompletely resected patients, P = NS. The remainder of the patients underwent distal pancreatectomy. There were no statistical differences in primary tumor size, lymph node metastases, or adjuvant treatments between patients with resected and unresected liver metastases. The median overall survival for the completely resected group was 78 months, longer than the 17 months for the group with unresectable liver metastases (P = 0.06). Complete tumor resection (or the tumor biology that allows such complete resection) affords a survival advantage to patients with metastatic islet cell tumors of the pancreas. Patterns of liver metastases from islet cell tumors, specifically multiple bilobar metastases that are not amenable to resection and/or ablation, predict a poor outcome despite resection of the primary pancreatic tumor.

Intracytoplasmic inclusions (including the so-called "rhabdoid" phenotype) in pancreatic endocrine tumors

The cytoplasm of pancreatic endocrine tumors (PET) can show a diverse range of appearances from clear, to oncocytic, to intracellular mucin accumulation, and the presence of intracytoplasmic inclusions. Intracytoplasmic eosinophilic inclusions can vary morphologically and the spectrum ranges from small, dot-like hyaline inclusions, to deeply acidophilic/eosinophilic ones that occupy almost the whole cytoplasm and displace the nucleus eccentrically: the so-called "rhabdoid" phenotype. The aim of this study was to analyze the frequency, morphology, behavior, and relationship to clinicopathological features of large intracytoplasmic inclusions, including the rhabdoid phenotype, in a large number of PET. The morphological features of 84 cases were assessed for the presence of large, globular intracytoplasmic inclusions. Fourteen of 84 cases contained intracytoplasmic inclusions with 5 cases containing cells conforming to the characteristic rhabdoid morphology. The remaining nine cases showed pale intracytoplasmic inclusions. Four of the five cases with rhabdoid cells had spread to lymph nodes and/or peripancreatic fatty tissue. This study confirms that a spectrum of large intracytoplasmic inclusions is encountered in PET, ranging from lightly eosinophilic intracytoplasmic globules to the more typical rhabdoid phenotype (deeply eosinophilic inclusions). This phenotype, in particular the rhabdoid cells, is worthy of attention as a proportion may show lymphovascular invasion with evidence of metastasis at the time of presentation, irrespective of size, mitotic rates, or necrosis.

Cytologic diagnosis of pancreatic endocrine tumors by endoscopic ultrasound-guided fine-needle aspiration: A review

Precise localization and diagnosis of pancreatic endocrine tumors (PETs) is important, because pancreatic PETs have different clinical and biological behavior and treatment modalities than do exocrine pancreatic tumors. In contrast to the much more common exocrine adenocarcinomas, cytologic studies of PET are relatively rare and many cytopathologists lack experience with the cytomorphologic features of these tumors.During the last 10 yr, endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) has matured into an accurate, highly sensitive, and cost-effective modality for the preoperative localization of pancreatic PETs. This has resulted in an increased number of PETs first sampled as cytology specimens. This manuscript focuses on the cytomorphologic features most suggestive of pancreatic PETs, differential diagnosis, and diagnostic pitfalls of PETs. The technical development of EUS-guided FNA and the ancillary studies for pancreatic PETs are also reviewed. The data summarized in this review indicate that EUS-FNA is a valuable method in the recognition of pancreatic PETs and in most cases cytopathologists could reach a correct diagnosis of these tumors, including their hormone producing capability on aspirated cytologic material.

Mixed exocrine-endocrine tumor of the pancreas

CONTEXT

Neoplasms of the pancreas usually show ductal, acinar or endocrine differentiation. Tumors with mixed exocrine and endocrine components are unusual. We herein describe a case of a mixed ductal-endocrine tumor.

CASE REPORT

A 65-year-old woman was referred to our department with a diagnosis of carcinoma of the tail of the pancreas. The patient had a short history of upper abdominal pain, nausea and melena. Upper gastrointestinal endoscopy revealed gastric fundus varices and CT scan demonstrated an inhomogeneous tumor located in the tail of the pancreas infiltrating the spleen and the splenic vein. The patient underwent distal pancreatectomy and splenectomy, and had an uneventful recovery. Pathological examination revealed a mixed ductal-endocrine tumor. The endocrine component was immunoreactive for glucagon, gastrin and somatostatin, and non-reactive for insulin.

CONCLUSIONS

Because of the rarity and unpredictable biologic behavior of these tumors, the need for adjuvant therapy has not yet been well-defined. The patient has had a follow-up CT scan every six months, and one and a half years later remains disease free.

Cyclin-dependent kinase (cdk6) and p16 in pancreatic endocrine neoplasms

AIMS

p16 and p27, the inhibitors of cyclin-dependent kinases, have been reportedly decreased in certain human tumours, including a few endocrine tumours. The current study used immunocytochemical staining to compare the staining intensity of cdk6 and its inhibitor, p16, in pancreatic endocrine neoplasms with normal pancreatic islets.

METHODS

Twenty-four primary pancreatic endocrine neoplasms, consisting of 12 insulinomas, one glucagomoma, three pancreatic polypeptide (PP)-omas, five gastgrinomas and three non-fuctioning tumours, were immunocytochemically studied for cdk6 and p16 compared with the adjacent non-neoplastic islets.

RESULTS

In the normal islets, cdk6 staining was strongly positive for islet cell nuclei and cytoplasms, whereas p16 was strongly positively stained for islet cell cytoplasms. Insulinomas, glucagonoma, PP-omas and non-functioning tumours were weakly stained for cdk6 and p16. Among five gastrinomas, three tumours were moderately stained and two tumours were more weakly stained for cdk6 and p16. Thus, tumour cells were weaker stained for cdk6 and p16 compared with the strong staining of normal islet cells. No distinct immunostaining difference was observed among five kinds of pancreatic endocrine neoplasms.

CONCLUSIONS

The decreased immunocytochemical staining for cdk6 and p16 is consistently observed in five kinds of pancreatic endocrine neoplasms. This decreased cdk6 and p16 in pancreatic endocrine neoplasms may be a part of the cell cycle event in tumour transformation and progression, and the same process may involve other endocrine tumours.

Fluorouracil, doxorubicin, and streptozocin in the treatment of patients with locally advanced and metastatic pancreatic endocrine carcinomas

PURPOSE

The role of systemic chemotherapy in the management of pancreatic endocrine carcinoma (islet cell carcinoma; PEC) is an area of considerable controversy. Response rates ranging from 6% to 69% have been reported for streptozocin-based chemotherapy. We retrospectively studied 84 patients with locally advanced or metastatic PEC who had been treated with fluorouracil, doxorubicin, and streptozocin (FAS) to determine the objective response rate, duration of progression-free survival (PFS), and duration of overall survival (OS).

PATIENTS AND METHODS

Eligible patients had histologic or cytologic confirmation of their tumor and measurable disease on computed tomography or magnetic resonance imaging scans. Response to treatment was evaluated in this study using the new international criteria proposed by the Response Evaluation Criteria in Solid Tumors Committee.

RESULTS

Sixty-one of the patients were male and 23 were female, with a median age of 54 years (range, 24 to 78 years). The response rate (RR) to FAS was 39%, with a median response duration of 9.3 months. The 2-year PFS rate was 41%, and the 2-year OS rate was 74%. The extent of liver metastatic disease correlated with a worse PFS (P = .01 by log-rank test) and a worse OS (P < .0001 by log-rank test). Analyses showed that metastatic replacement of more than 75% of the liver and prior chemotherapy were independently associated with inferior PFS.

CONCLUSION

Patients with locally advanced or metastatic PEC who are treated with FAS may have a reasonable RR, and responders may experience longer PFS and OS. The volume of metastases in the liver is the most important predictor of outcome.

Two cases of pancreatic neoplasia in British ferrets (Mustela putorius furo)

Two six-year-old male neutered polecat ferrets (Mustela putorius furo) were presented for the investigation of acute collapse or periodic weakness and weight loss. While blood biochemistry revealed hypoglycaemia in both cases, diagnosis of an insulin-secreting neoplasia was confirmed by exploratory surgery in one case and supported by the use of an insulin assay in the other. Subsequent histopathological examination showed the former to be a pancreatic islet cell carcinoma and the latter to be a pancreatic islet cell adenoma. While neoplasia of the pancreas commonly affects ferrets in the USA, there appears to be only one previous report from the UK.

Endoscopic ultrasonography of nonfunctioning pancreatic islet cell tumors with histologic correlation

BACKGROUND/AIMS

Preoperative differentiation of benign and malignant pancreatic nonfunctioning islet cell tumors remains problematic. The present study aimed to evaluate endoscopic ultrasonography (EUS) features of benign and malignant tumors with histologic correlation.

METHODOLOGY

Ten patients with surgically resected nonfunctioning pancreatic islet cell tumors were retrospectively reviewed.

RESULTS

EUS demonstrated a homogenous hypoechoic (n=2) or hyperechoic (n=1) mass in the 3 benign tumors. EUS showed a hypoechoic mass with an irregular central hyperechoic portion (n=4), a hyperechoic mass with an irregular central hypoechoic portion (n=1), a cystic mass with a large irregular internal hypoechoic portion (n=1), or a hypoechoic mass within the entire lumen of the main pancreatic duct (MPD) (n=1) in the 7 malignant tumors. Histologically, the irregular central portions of the malignant tumors corresponded to necrosis, hemorrhage, fibrosis with hyalinosis, cystic degeneration, and/or calcification. Complete obstruction of the main pancreatic duct on EUS was observed in the 2 malignant tumors. The echogenicity of the tumors was closely associated with arrangement of tumor cells and quantity of fibrous stroma.

CONCLUSIONS

Heterogeneous internal structures and complete obstruction of the main pancreatic duct are considered as important EUS features that are suggestive of malignancy in nonfunctioning pancreatic islet cell tumors.

Laparoscopic resection of a pancreatic polypeptidoma with a solitary liver metastasis

Pancreatic neuroendocrine tumor is an uncommon disease, and surgery is the only potentially curative treatment even when there is hepatic metastasis. A patient undergoing concomitant laparoscopic distal pancreatectomy and hepatectomy for pancreatic polypeptidoma with a solitary liver metastasis is reported.

DPC4/Smad4: no mutations, rare allelic imbalances, and retained protein expression in pancreatic endocrine tumors

Several chromosomal loci involved in tumorigenesis of pancreatic endocrine tumors (PET) have been identified. To date, the only gene known to be frequently altered is the MEN1 gene. Recently, DPC4 mutations and homozygous deletions have been described in 5/9 (55%) non-functioning PET, thus representing the most frequent genetic aberration described in PET. However, these data are in discordance with comparative genomic hybridization (CGH) results that rarely show genetic losses on chromosome 18. They have also been challenged by immunohistochemical data. We performed a detailed combined DPC4 mutation and deletion analysis in 34 benign and malignant PET. Mutations of the conserved C-terminal exons were not found in all examined PET and allelic loss (LOH) was found to be rare (<6%) by combined microsatellite PCR and FISH analysis. In addition, DPC4 protein expression was retained in all PET that were examined by immunohistochemistry. Therefore, DPC4 inactivation by mutation or deletion appears to be very rare in PET, which confirms the current concept of unrelated mechanisms of tumorigenesis of endocrine versus exocrine pancreatic tumors.

Management of nonfunctioning islet cell tumors

AIM: To more clearly define the clinical and pathological characteristics and appropriate diagnosis and treatment of nonfunctioning (NFICTs) islet cell tumors, and to review our institutional experience over the last 30 years.

METHODS: The records of 43 patients confirmed to have nonfunctioning islet cell tumors of pancreas were retrospectively reviewed. Survival was estimated by the Kaplan-Meier methods and potential risk factors for survival were compared with the log-rank tests.

RESULTS: The mean age was 31.63 years (range, 8 to 67 years). There were 7 men and 36 women. Twenty-eight patients had a confirmed diagnosis of nonfunctioning islet cell carcinoma (NFICC) and benign islet cell tumors were found in 15 patients. The most common symptoms in patients with NFICTs were abdominal pain (55.8%), nausea and/or vomiting (32.6%), fatigue (25.6%) and abdominal mass (23.3%). Preoperative ultrasonic and computed tomography localized the tumors in all patients. Forty-three NFICTs were distributed throughout the pancreas, with 21 located to the right of the superior mesenteric vessels, 10 in the body of the pancreas, 6 in the tail of the pancreas, and multiple tumors were found in one patient. Thirty-nine of 43 patients (91%) underwent surgical resection. Surgical treatment was curative in 30 patients (70%) and palliative in 9 (21%). The resectability and curative resection rate in patients with NFICC of pancreas were 89% and 61%, respectively. The overall cumulative 5-year and 10-year survival rates for patients with NFICC were 58.05% and 29.03%, respectively. Radical operation and diameter of cancer small than 10 cm were positive prognostic factors in females younger than 30 years old. Multivariate Cox regression analysis indicated that radical operation was the only independent prognostic factor, P = 0.007.

CONCLUSION: Nonfunctioning islet cell tumors of pancreas are found mainly in young women. The long-term results for patients undergone surgery, especially curative resection are good.

Intraductal growth of a nonfunctioning endocrine tumor of the pancreas

Intraductal growth of nonfunctioning endocrine tumors of the pancreas may be very rare, and our survey of literature shows only two cases have been described. We report a case of a 43-year-old man with a nonfunctioning endocrine tumor of the pancreas that uniquely grew within the lumen of the main pancreatic duct (MPD) without ductal involvement and completely obstructed the MPD. Endoscopic ultrasonography (EUS) and endoscopic retrograde cholangiopancreatography (ERCP) were very helpful to delineate the intraductal growth of the tumor and to determine the resection line of the pancreas. A nonfunctioning pancreatic endocrine tumor is important to consider on differential diagnoses when complete obstruction of the MPD is demonstrated on ERCP. It is speculated that the tumor originated from precursor cells of the pancreatic duct or islet cells adjacent to the MPD and slowly proliferated within the lumen of the MPD.

Diagnosis and treatment of malignant pancreatic endocrine tumour

OBJECTIVE

To summarize our experience in the diagnosis and treatment of malignant pancreatic endocrine tumour.

METHODS

We retrospectively reviewed 36 cases of malignant pancreatic endocrine tumours in our hospital from July 1987 to April 2002, and summarized its clinical features.

RESULTS

Liver metastasis was the main malignant manifestation of malignant pancreatic endocrine tumours (incidence rate 72.2%). Removals of primary lesion and isolated hepatic metastatic lesion were means of curative therapy. Interventional chemotherapy was an important adjuvant treatment.

CONCLUSION

Comprehensive therapy plays an important role in improving the prognosis of malignant pancreatic endocrine tumour.

Cathepsin cysteine proteases are effectors of invasive growth and angiogenesis during multistage tumorigenesis

Tumors develop through successive stages characterized by changes in gene expression and protein function. Gene expression profiling of pancreatic islet tumors in a mouse model of cancer revealed upregulation of cathepsin cysteine proteases. Cathepsin activity was assessed using chemical probes allowing biochemical and in vivo imaging, revealing increased activity associated with the angiogenic vasculature and invasive fronts of carcinomas, and differential expression in immune, endothelial, and cancer cells. A broad-spectrum cysteine cathepsin inhibitor was used to pharmacologically knock out cathepsin function at different stages of tumorigenesis, impairing angiogenic switching in progenitor lesions, as well as tumor growth, vascularity, and invasiveness. Cysteine cathepsins are also upregulated during HPV16-induced cervical carcinogenesis, further encouraging consideration of this protease family as a therapeutic target in human cancers.

Expression of interleukin-8 in human obstructive pancreatitis

CONTEXT

Obstructive pancreatitis is a specific form of pancreatitis, which is caused by the obstruction of the main pancreatic duct due to tumors or some other causes. Interleukin-8 is induced in acute pancreatitis, but its expression in obstructive pancreatitis has not been clarified.

OBJECTIVE

We attempted to provide some insight into the significance of interleukin -8 in the pathogenesis of pancreatic fibrosis.

PATIENTS

Fifteen cases of pancreatic cancer, 7 cases of mucinous cystadenoma, 3 cases of Vater's papilla cancer and 9 normal pancreases were included in this study.

MAIN OUTCOME MEASURES

The obstructive pancreatitis portions of the above pathologies were evaluated for interleukin-8 expression by means of immunohistochemistry and in situ hybridization.

RESULTS

Interleukin-8 was positive in 72% of cases of obstructive pancreatitis. The positive rate was not significantly related to the etiology of the obstruction (P=0.972). Interleukin-8 was expressed in infiltrating cells, proliferating ductular cells and acinar cells. In contrast, normal pancreases and tumor cells lacked interleukin-8 expression (P<0.001 vs. obstructive pancreatitis). Both immunohistochemistry and in situ hybridization demonstrated that interleukin-8 was expressed mostly in acinar cells in mild pancreatic fibrosis, whereas it was expressed in stromal and ductular cells in moderate and severe pancreatic fibrosis.

CONCLUSIONS

These results suggest that interleukin-8 expression is related to the fibrotic process in obstructive pancreatitis.

Clear cell endocrine tumor of the pancreas which is not associated with von Hippel-Lindau disease: report of a case

We describe the case of a pancreatic endocrine tumor with marked clear cell changes. The patient, a 56-year-old woman, presented with appetite loss and nausea but no evidence of either von Hippel-Lindau disease, or a family history of the disease. A radiological examination revealed a hypervascular tumor measuring 5.2 cm in diameter located in the pancreatic head. The patient underwent a pylorus-preserving pancreatoduodenectomy. The cut surface of the tumor was yellowish and well demarcated. Histologically, the tumor was composed of cuboidal cells with clear cytoplasm, thus forming trabecular and insular nests. Immunohistochemically, the tumor cells were strongly positive for chromogranin. An electron microscopic examination revealed the tumor cells to contain neuroendocrine secretory granules, abundant lipid droplets, and some crystalloid bodies in the cytoplasm. We conclusively diagnosed it to be a pancreatic clear cell endocrine tumor. Such tumors not associated with von Hippel-Lindau disease are extremely rare.

Protein 4.1B in mouse islets of Langerhans and beta-cell tumorigenesis

Protein 4.1 family proteins are thought to interact with membrane proteins and membrane skeletons. Immunohistochemical studies by light and electron microscopy were performed on mouse pancreas with a specific antibody against protein 4.1B. Specific protein 4.1B immunolabeling was observed on endocrine cells in the islets of Langerhans. Protein 4.1B localized along the plasma membranes facing adjacent cells. By immunoelectron microscopy, the immunolabeling of the cells was restricted to the cytoplasmic side just beneath their plasma membrane, including the membranes adjacent to neighboring cells, while the plasma membranes facing endothelial cells were not immunolabeled for protein 4.1B. The immunolocalization of E-cadherin was similar, if not identical, to that of protein 4.1B supporting the idea that protein 4.1B may be functionally interconnected with adhesion molecules. In a transgenic mouse model of pancreatic beta-cell carcinogenesis (Rip1Tag2), the loss of protein 4.1B expression coincided with the phenotypic transition from adenoma to carcinoma. Therefore, we propose a role of protein 4.1B as a connecting and/or signaling molecule between membrane architecture, cell adhesion, and tumor cell invasion in mouse pancreatic endocrine cells.

Morphological and functional investigations of neuroendocrine tumors of the pancreas

Neuroendocrine tumors of the pancreas are rare neoplasms arising predominantly from the pancreatic islets of Langerhans and are thus known as islet cell tumors. More than the half of all neuroendocrine tumors are called functioning islet cell tumors because they secrete one or more biologically active peptides that may produce clinical symptoms. Clinical diagnosis of non-functioning, i.e., biologically inactive, tumors is often delayed and patients tend to present with advanced tumors (size greater than 5 cm) that are easily localized by using conventional imaging modalities. On the other hand, symptoms of functioning islet cell tumors usually appear early in the clinical course, rendering the preoperative localization of these small hormone-producing tumors (size less than 2 cm) difficult with non-invasive methods. Since functioning islet cell tumors can often be cured by surgical resection, invasive procedures are warranted when necessary for localization diagnosis. Failure to search for, detect, and resect these small tumors will invariably result in persistent symptoms. Regarding the unsatisfactory results of morphological imaging methods, functional studies, especially arterial stimulation with hepatic venous samplings, may provide a preoperative regionalization of the pancreatic adenoma, regardless of its size.

Benefits of targeting both pericytes and endothelial cells in the tumor vasculature with kinase inhibitors

Functions of receptor tyrosine kinases implicated in angiogenesis were pharmacologically impaired in a mouse model of pancreatic islet cancer. An inhibitor targeting VEGFRs in endothelial cells (SU5416) is effective against early-stage angiogenic lesions, but not large, well-vascularized tumors. In contrast, a kinase inhibitor incorporating selectivity for PDGFRs (SU6668) is shown to block further growth of end-stage tumors, eliciting detachment of pericytes and disruption of tumor vascularity. Importantly, PDGFRs were expressed only in perivascular cells of this tumor type, suggesting that PDGFR(+) pericytes in tumors present a complimentary target to endothelial cells for efficacious antiangiogenic therapy. Therapeutic regimes combining the two kinase inhibitors (SU5416 and SU6668) were more efficacious against all stages of islet carcinogenesis than either single agent. Combination of the VEGFR inhibitor with another distinctive kinase inhibitor targeting PDGFR activity (Gleevec) was also able to regress late-stage tumors. Thus, combinatorial targeting of receptor tyrosine kinases shows promise for treating multiple stages in tumorigenesis, most notably the often-intractable late-stage solid tumor.

Ductulo-insular pancreatic endocrine neoplasms: clinicopathologic analysis of a unique subtype of pancreatic endocrine neoplasms

Pancreatic neoplasms with mixed ductal and endocrine components are a heterogeneous group of tumors. The least recognized of these are pancreatic endocrine tumors (PETs) displaying benign-appearing tumor-associated ductules. To characterize these ductulo-insular pancreatic endocrine tumors (DI-PETs), we reviewed a series of 92 resected PETs. To be considered as a DI-PET we required the presence and tight intermingling of ductules with the dominant endocrine component (including the presence of ductulo-insular units). A total of 15 PETs fulfilled our criteria (16.3%). The average age of the DI-PET patients was similar to typical PETs (54 years vs 56 years). These tumors were smaller and more often insulin positive than typical PETs (p <0.05). Diffuse stromal fibrosis was more frequent in DI-PETs (11 of 15; 73.3.7%) compared with PETs (8 of 72; 11.1%) (p <0.05). The tumor-associated ductules were composed of cuboidal cells with dense eosinophilic cytoplasm and round nuclei without atypia or mitoses. They were positive for cytokeratin 7 and cytokeratin 19 and lacked any neuroendocrine markers. Reversibly, the endocrine component was negative for cytokeratin 7 and cytokeratin 19 and positive for neuroendocrine markers. Ultrastructural examination of ductulo-insular units confirmed a dual ductal and endocrine differentiation with amphicrine differentiation in one case. Follow-up was available in 12 cases with an average follow-up of 70.1 months (range 25-203 months). Ten patients are currently alive, and two patients died 81 and 158 months after surgery. We conclude that DI-PETs are not uncommon and that they are biologically similar to other PETs. We also hypothesize that the ductal cells develop by transdifferentiation of the endocrine cells.

Low nuclear proliferative activity is associated with nonmetastatic islet cell tumors

CONTEXT

Traditional morphologic features of tumor aggression are of limited value in predicting the malignant behavior of endocrine neoplasms. We explored the potential value of nuclear proliferative activity (using Ki-67 immunostaining with semiquantitative scoring) in predicting the clinical behavior of pancreatic islet cell tumors (ICTs), and we correlated this characteristic with hormone expression.

OBJECTIVE

To evaluate whether Ki-67 immunostaining using a semiquantitative scoring system has value in predicting the clinical behavior of pancreatic ICTs.

DESIGN

We studied 39 pancreatic ICTs from 39 patients. Twenty-two ICTs did not metastasize in a median follow-up period of 91 months. The remaining 17 neoplasms did produce metastases (8 in liver, 7 in regional lymph nodes, and 2 in peritoneum). Immunohistochemistry was performed using antibodies to Ki-67 and pancreatic hormones (insulin, glucagon, gastrin, somatostatin, pancreatic polypeptide, vasoactive intestinal polypeptide, and corticotropin). A semiquantitative Ki-67 grading system was followed. The nuclear proliferative activity, as determined by a positive reaction for Ki-67, was considered low (<5% of cells staining positively), intermediate (5%-25% of cells staining positively), or high (>25% of cells staining positively).

RESULTS

The majority of the nonmetastatic ICTs (16 cases, 73%) demonstrated either negative or low staining for Ki-67 (P <.001). Conversely, all metastatic ICTs expressed at least an intermediate-grade reaction. High nuclear proliferative activity was only seen in metastatic neoplasms (3 cases, 17%). There was no relationship between immunoexpression of pancreatic hormones and nuclear proliferative activity by either group of tumors.

CONCLUSION

An ICT with low nuclear proliferative activity is unlikely to metastasize, whereas high proliferative activity is associated with a metastatic phenotype. Immunohistochemical assessment of Ki-67 using a semiquantitative scoring system is a simple and reliable detection method of cellular proliferative activity in ICTs of the pancreas.