Genetic evidence for the multi-step progression of mixed glandular-neuroendocrine gastric carcinomas

Primary small cell neuroendocrine carcinoma of the kidney: morphological, immunohistochemical, ultrastructural, and cytogenetic study of a case and review of the literature

Poorly differentiated neuroendocrine carcinomas (PDNECs) of the kidney are extremely rare high-grade cancers accounting for only 42 cases reported in the literature. In this paper, we describe the morphological, immunohistochemical, ultrastructural, and for the first time, cytogenetic features of a renal PDNEC. In addition, we have reviewed the literature and compared the published clinicopathological data with our morphological and genetic results. The tumor arose within the kidney parenchyma and showed the typical histological features of a pure small cell PDNEC. Fluorescence in situ hybridization study demonstrated a complex chromosomal assessment indicative of a high degree of chromosome instability with gain of multiple chromosomes, loss of p53, and amplification of myc gene. These results suggest that renal PDNEC has a different genetic background to renal clear cell carcinoma, mainly characterized by the loss of the short arm of chromosome 3. Conversely, genetic alterations seem to resemble those of type 2 papillary renal cell carcinoma. The review of the literature demonstrated that PDNECs are associated with poor prognosis and that parenchymal tumors show some differences from those arising in the pelvis, in that parenchymal tumors are purely neuroendocrine while pelvic tumors are mostly mixed neuroendocrine-exocrine neoplasms.

A composite adenoendocrine carcinoma of the stomach arising from a neuroendocrine tumor

Gastric neuroendocrine tumors (carcinoids) are relatively uncommon neoplasms. Some 70 to 80% of these lesions occur in patients with autoimmune body gastritis. This disorder, however, is also a risk factor for the development of conventional gastric adenocarcinomas. We report a case of a patient with autoimmune body gastritis and a well-differentiated neuroendocrine tumor of the stomach, which was removed with endoscopic full-thickness resection in sano upon signs of invasive growth several years after its first diagnosis. Histological examination surprisingly showed a composite glandular-endocrine gastric carcinoma. We discuss the histopathological genesis of the tumor and provide evidence that endoscopic full-thickness resection might be an oncologically appropriate minimally invasive treatment for such gastric lesions.

Relation of neuroendocrine cells to transforming growth factor-alpha and epidermal growth factor receptor expression in gastric adenocarcinomas: prognostic implications

The presence of neuroendocrine (NE) cells in gastric adenocarcinoma (GCa) is well documented, however, their significance is controversial. There is no evidence in the literature concerning the possible effect of these cells on the expression of TGF-alpha and EGFR, which are believed to confer growth advantage to tumor cells. 101 partial or total gastrectomy specimens from patients operated for conventional gastric adenocarcinoma were included in the study. In each case immunohistochemistry was performed on sequential tissue sections for chromogranin A (ChrA), TGF-alpha and EGFR. Samples were graded based on the number of ChrA-positive cells (0-3). TGF-alpha and EGFR expressions were evaluated according to both the intensity (0-2) and quantification of the positively stained areas (0-3). Follow-up data was available in 54 patients. Twenty-seven patients died of disease, while 27 patients were alive with a follow-up of at least 15 months. ChrA expression was detected in 54.4% of the tumor specimens. TGF-alpha was stained positively in 42.6% and EGFR in 49.5% of the cases. NE cells in GCa was related to TGF-alpha (p<0.0001) and EGFR expression (p<0.05), and TGF-alpha/EGFR coexpression (p<0.001). Among histopathologic variables, the presence of NE cells was significantly related to grade, stage and lymph node status. Although the presence of NE cells had no effect on survival, the expression of EGFR (p<0.0001) and TGF-alpha (p=0.002) were related to survival. The results of our study suggest that the presence of NE cells may have an effect on the expression of TGF-alpha and EGFR in GCa, and the autocrine mechanism between TGF-alpha and EGFR plays an important role in the prognosis of gastric carcinoma.

Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms

Within the spectrum of neuroendocrine tumors arising in different organs, intermediate and controversial entities exist displaying a coexistence of neuroendocrine and nonneuroendocrine cell populations, and that are grouped under terms such as "goblet cell carcinoid", "mixed endocrine-exocrine carcinoma", "combined carcinomas", or "adenocarcinoma with neuroendocrine differentiation". These tumors may display variable amounts of the two components, potentially ranging from 1 to 99%, and variable structural patterns, ranging from single scattered neuroendocrine cells to a well-defined neuroendocrine tumor cell component organized in typical organoid, trabecular, or solid growth patterns. Although variably included in the site-specific World Health Organization classification schemes, clear definitions and diagnostic features are still missing, as well as a definite knowledge of their biological properties and histogenesis. In the present report, the main characteristics of tumors showing mixed neuroendocrine and nonneuroendocrine features will be described, using morphological patterns and site of origin as schematic guidelines. Moreover, molecular and clinical aspects, which might help to understand their possible histogenesis and biological behavior, will be reviewed.

[Mixed endocrine tumors]

Mixed endocrine tumors are tumors composed of at least two distinct tumor populations, one of which is endocrine. Because of their rarity and unusual presentation, endocrine mixed tumors raise many problems of diagnosis, management and therapy. Three main types of endocrine mixed tumors are recognized: The existence of these various types has been confirmed by recent molecular studies, even if the same studies have also shown that the histogenesis of a mixed endocrine tumor cannot be predicted from its histological features. Composite tumors are the less rare mixed tumors. The recent WHO classification recommends to restrict the term of composite endocrine tumor to the epithelial tumors containing at least 30% of obviously tumoral endocrine cells; some authors recommend to use higher thresholds, of at least 50%, in order to avoid overdiagnosis. The endocrine component is usually well differentiated, easily identified by its suggestive histological features; the endocrine nature of tumor cells is confirmed by the immunodetection of specific endocrine and neuro-endocrine markers (such as chromogranin A and synaptophysin). In some cases, the endocrine component is poorly differentiated: the demonstration of neuro-endocrine markers is necessary to confirm the diagnosis. Mixed tumors can occur in every anatomical site; they are more frequent in organs containing endocrine cells in the normal state (especially the digestive tract and the pancreas), but they can also be observed in organs devoid of endocrine cells (such as the mammary gland). The management of mixed endocrine tumors must take into account the more aggressive component. Mixed tumors containing a well differentiated endocrine component and an adenocarcinomatous component are to be treated like adenocarcinomas. Mixed tumors containing a poorly differentiated endocrine component must be considered as poorly differentiated endocrine carcinomas.

The 5'-end transitional CpGs between the CpG islands and retroelements are hypomethylated in association with loss of heterozygosity in gastric cancers

Background

A loss of heterozygosity (LOH) represents a unilateral chromosomal loss that reduces the dose of highly repetitive Alu, L1, and LTR retroelements. The aim of this study was to determine if the LOH events can affect the spread of retroelement methylation in the 5'-end transitional area between the CpG islands and their nearest retroelements.

Methods

The 5'-transitional area of all human genes (22,297) was measured according to the nearest retroelements to the transcription start sites. For 50 gastric cancer specimens, the level of LOH events on eight cancer-associated chromosomes was estimated using the microsatellite markers, and the 5'-transitional CpGs of 20 selected genes were examined by methylation analysis using the bisulfite-modified DNA.

Results

The extent of the transitional area was significantly shorter with the nearest Alu elements than with the nearest L1 and LTR elements, as well as in the extragenic regions containing a higher density of retroelements than in the intragenic regions. The CpG islands neighbouring a high density of Alu elements were consistently hypomethylated in both normal and tumor tissues. The 5'-transitional methylated CpG sites bordered by a low density of Alu elements or the L1 and LTR elements were hypomethylated more frequently in the high-level LOH cases than in the low-level LOH cases.

Conclusion

The 5'-transitional methylated CpG sites not completely protected by the Alu elements were hypomethylated in association with LOH events in gastric cancers. This suggests that an irreversible unbalanced decrease in the genomic dose reduces the spread of L1 methylation in the 5'-end regions of genes.

Relationship between the extent of chromosomal losses and the pattern of CpG methylation in gastric carcinomas

The extent of unilateral chromosomal losses and the presence of microsatellite instability (MSI) have been classified into high-risk (high- and baseline-level loss) and low-risk (low-level loss and MSI) stem-line genotypes in gastric carcinomas. A unilateral genome-dosage reduction might stimulate compensation mechanism, which maintains the genomic dosage via CpG hypomethylation. A total of 120 tumor sites from 40 gastric carcinomas were examined by chromosomal loss analysis using 40 microsatellite markers on 8 chromosomes and methylation analysis in the 13 CpG (island/non-island) regions near the 10 genes using the bisulfite-modified DNAs. The high-level-loss tumor (four or more losses) showed a tendency toward unmethylation in the Maspin, CAGE, MAGE-A2 and RABGEF1 genes, and the other microsatellite-genotype (three or fewer losses and MSI) toward methylation in the p16, hMLH1, RASSF1A, and Cyclin D2 genes (p<0.05). The non-island CpGs of the p16 and hMLH1 genes were hypomethylated in the high-level-loss and hypermethylated in the non-high-level-loss sites (p<0.05). Consequently, hypomethylation changes were related to a high-level loss, whereas the hypermethylation changes were accompanied by a baseline-level loss, a low-level loss, or a MSI. This indicates that hypomethylation compensates the chromosomal losses in the process of tumor progression.

Composite glandular-endocrine cell carcinomas of the stomach: clinicopathologic and methylation study

Four cases of very rare composite glandular-endocrine cell carcinoma of the stomach are presented with methylation findings. All but one of the tumors arose in the antrum and two of them were at the early stage. Each composite carcinoma was accompanied by atrophic and metaplastic gastritis in the adjacent mucosa. Three cases showed lymph nodes metastasis, and one of them showed both glandular and neuroendocrine tumor components within the metastatic nodes. Mucin stains were positive in the adenocarcinoma areas while only the neuroendocrine markers were positive in neuroendocrine tumor components. Of all seven markers tested for, p16INK4A methylation was observed in both components of one composite carcinoma and hMLH1 was methylated in the neuroendocrine tumor component within the same tumor. An additional six gastric large cell neuroendocrine carcinomas showed no methylation. Follow up of patients indicated short survival in patients with poorly differentiated neuroendocrine carcinoma components and advanced stages of tumors, while patients with well-differentiated neuroendocrine tumor components and early stages showed long disease-free survival. Our results suggest that hypermethylation of tumor suppressor genes is rare in gastric composite and neuroendocrine carcinomas, and prognosis of gastric composite carcinomas appears to be related to the histopathology of neuroendocrine components and tumor stage.

Hepatobiliary neuroendocrine carcinoma in cats: a clinicopathologic, immunohistochemical, and ultrastructural study of 17 cases

Hepatobiliary neuroendocrine carcinoma was diagnosed in 17 cats in a period of 10 years. Seven tumors were of intrahepatic origin, one of which was a composite containing components of epithelial and neuroendocrine carcinoma. Nine tumors were of extrahepatic origin, and one tumor was located in the gall-bladder. The cats were adult and geriatric, and the male : female ratio varied according to tumor group. Hepatomegaly, anorexia, weight loss, and vomiting were the most common clinical signs observed in the cats with hepatic neuroendocrine carcinoma. The cats with extrahepatic neuroendocrine carcinoma showed these signs plus icterus (5/9) and high concentrations of hepatic enzymes. Histologically, the hepatic neuroendocrine carcinomas had two patterns, one with acinar structures separated by vascular stroma lined by cuboidal or columnar cells and the other solid with groups of anaplastic cells separated by vascular stroma. The composite tumor consisted of both bile duct carcinoma and neuroendocrine carcinoma. The extrahepatic neuroendocrine carcinomas and the gallbladder neuroendocrine carcinoma were characterized by solid sheets or groups of round to oval cells with vascular or fibrovascular stroma. Immunohistochemical examination of 10 of the neuroendocrine carcinomas revealed that all 10 stained with neuron-specific enolase; one bile duct carcinoma and the gallbladder carcinoma stained with chromogranin; four of five bile duct carcinomas and the gall bladder carcinoma stained with synaptophysin; and one bile duct carcinoma stained with gastrin. One cat with hepatic carcinoma had duodenal ulcer; in this cat, ultrastructural studies showed neurosecretory granules leading to the diagnosis of Zollinger-Ellison syndrome. In four cats in which necropsy was permitted, carcinomatosis (4/4), lymph nodes (4/4), lungs (2/4), and intestines (1/4) were the metastatic sites. Fourteen of the 17 cats were euthanatized during or immediately after surgery.

Drastic down-regulation of Krüppel-like factor 4 expression is critical in human gastric cancer development and progression

Krüppel-like factor 4 (KLF4) is highly expressed in epithelial tissues such as the gut and skin. However, the role of KLF4 in human gastric cancer development and progression is unknown. Here we show that KLF4 protein expression was decreased or lost in primary tumors and, in particular, lymph node metastases when compared with that in normal gastric mucosa. Moreover, loss of KLF4 expression in the primary tumors was significantly associated with poor survival, and also an independent prognostic marker in a multivariate analysis. Consistently, most human gastric cancer cell lines exhibited loss of or a substantial decrease in KLF4 expression at both RNA and protein levels. Enforced restoration of KLF4 expression resulted in marked cell growth inhibition in vitro and significantly attenuated tumor growth and total abrogation of metastasis in an orthotopic animal model of gastric cancer. Mechanism studies indicated that promoter hypermethylation and hemizygous deletion contributed to the down-regulation of KLF4 expression and the induction of apoptosis contributed to the antitumor activity of KLF4. Collectively, our data provide first clinical and casual evidence and potential mechanism that the alteration of KLF4 expression plays a critical role in gastric cancer development and progression.

Allelotypes and Fluorescence In situ Hybridization Profiles of Poorly Differentiated Endocrine Carcinomas of Different Sites

PURPOSE

The aim of this work was to investigate the genotypic profiles of 36 poorly differentiated endocrine carcinoma (PDEC) of different sites to verify if their very similar phenotype may reflect similar pattern of genetic anomalies and if useful diagnostic or prognostic markers may be pointed out.

EXPERIMENTAL DESIGN

All tumors were microallelotyped at 57 microsatellite on 11 autosomes and the allelotypes of a selected panel of tumors were validated by interphasic fluorescence in situ hybridization with centromeric probes for chromosomes 1, 3, 6, 11, 17, and 18 and a probe specific for p53.

RESULTS

Regardless of the primary sites, PDECs exhibit very complex allelotypes (86%) and TP53 allelic imbalance (89%). Among these cases, fluorescence in situ hybridization analysis confirmed the presence of multiple aneusomies and a chromosome instability phenotype. Very low percentage of allelic imbalance (AI) and few aneuploidies were detected in only five PDECs for which an overall longer survival was observed. We found recurrent AI on 3p, 5, and 11q13 in lung PDECs, on 5q21, 8p, and 18q21 in colorectal PDECs and on 7 and 11q22 in gastric PDECs. Significantly better outcome was observed in patients with PDEC exhibiting 8q AIs and absence of AI at chromosome regions 6q25 and 6p.

CONCLUSIONS

The concurrence of p53 inactivation and aneuploidies or chromosome instability are the main features of PDECs. However, the specific allelotypes observed in relation to primary site support the hypothesis that PDECs and exocrine carcinomas of all sites may share early pathogenetic mechanisms. Molecular markers of potential diagnostic and prognostic values for PDECs of different sites have been identified.

Histological and immunohistochemical study of composite neuroendocrine-exocrine carcinomas of the stomach

Composite neuroendocrine-exocrine carcinomas (NEECs) with two distinct components of adenocarcinoma and neuroendocrine (NE) carcinoma within the same tumor are rare but may have a clue for clarifying the pathogenesis of NE tumors arising from non-endocrine organs. This study was done to characterize histological and immunohistochemical features of NEECs of the stomach comparing with pure NE tumors of the gastrointestinal (GI) tract. Microscopically, adenocarcinoma components in 6 of 8 NEECs were well differentiated and located superficially, whereas NE components were poorly differentiated and located deeply. In the remaining two cases, smaller NE components were intermingled within adenocarcinoma components. Immunohistochemically, neural cell adhesion molecule (NCAM) was positive in 5 NE components, of which 3 cases were homogeneously positive, and 2 adenocarcinoma components of 8 NEECs, while 19 of 21 pure NE tumors of GI tract were homogeneously positive for NCAM. Ghrelin-immunoreactivity was found in 4 NE components and 2 adenocarcinoma components of NEECs, although 20 pure NE tumors were positive for ghrelin. Smad4 was positive in both components of 7 NEECs. These findings suggest that composite NEECs and pure NE tumors of GI tract may have different NE properties and that most NE components of composite NEECs of the stomach may originate from an adenocarcinoma precursor cell and occasional tumors from a pluripotent cell.

Primary Mixed Adenocarcinoma and Small Cell Carcinoma of the Appendix

Appendiceal carcinoids range from well-differentiated endocrine tumor to well-differentiated endocrine carcinoma, while poorly differentiated (small cell) carcinoma has not been described in this site. We report herein a case of mixed intestinal-type adenocarcinoma associated with a small cell carcinoma arisen in a 35-year-old woman and clinically presenting as an appendiceal abscess. The resected tumor histologically appeared as a biphasic lesion composed of a nonmucinous adenocarcinoma closely juxtaposed with a poorly differentiated (small cell) endocrine carcinoma. The subsequent right hemicolectomy was unremarkable, but one pericolic lymph node showed a metastatic deposit consisting of the adenocarcinoma only. The patient thus underwent a chemotherapeutic protocol for colorectal cancer, and she is alive and well at the 65-month follow-up. Immunohistochemically, the adenocarcinoma strongly stained for cytokeratin 20 and carcinoembryonic antigen, while the endocrine component displayed a dot-like positivity for pan-cytokeratins and chromogranin. Of note, both components did not stain with CDX2 and p53. At genotypic analysis by microsatellite instability, both components shared many microsatellite alterations as well as a normal p53 gene setup, although small cell carcinoma harbored additional alterations. Clinical and molecular findings led us to consider this lesion as a clonal tumor in which the endocrine component seems to derive from a progressive differentiation of the adenocarcinoma following a glandular-to-endocrine sequence.

Mixed acinar-endocrine carcinoma of the pancreas. A clinicopathological study and comparison with acinar-cell carcinoma

We compared the clinicopathological features of acinar-cell carcinomas (ACCs) with those of mixed acinar-endocrine carcinomas (MAECs). Specimens from 37 patients with ACC and 6 patients with MAEC were examined histologically and immunohistochemically. The mean age of ACC and MAEC patients was similar (61.3 years versus 58.4 years), but the sex ratio differed (ACC, 29 males and 8 females; MAEC, 2 males and 4 females). The size of the tumor was large in both cases (ACC, 13.8 cm in diameter; MAEC, 8.2 cm). Immunohistochemically, more than half of the tumor cells in all tumors, whether ACC or MAEC, stained for trypsin. In 20 of the 37 ACCs (54%), scattered endocrine cells (SECs) were found, which stained positively for synaptophysin (SYN) and/or chromogranin A (CGA). Interestingly, there was also a difference in the sex ratio between ACC patients without SECs (16 males and 1 female) and ACC patients with SECs (13 males and 7 females). In MAECs, the cells staining for SYN were more common than those staining for CGA and made up more than one-third of the neoplastic-cell population. In all but one case (in which the endocrine component was arranged in islet-like cell clusters), the endocrine cells were intimately mixed with trypsin-positive tumor cells. The endocrine cells only rarely expressed one of the known pancreatic or gastrointestinal hormones. Both ACCs and MAECs had a high proliferation rate and lacked p53 overexpression or progesterone and estrogen receptors. This study revealed that ACCS and MAECs share most clinicopathological features and, therefore, may form a single tumor entity, though they differ in the number of endocrine cells. The frequent identification of endocrine cells in these tumors suggests the existence of a pluripotent cell of origin that is capable of differentiating into acinar and endocrine cells.

Preoperative genetic diagnosis of gastric carcinoma based on chromosomal loss and microsatellite instability

The degree of chromosomal losses and the presence of microsatellite instability (MSI) in gastric carcinomas have been categorized into low-risk (low-level loss and MSI) and high-risk (baseline- and high-level losses) genotypes. With the aim of making a preoperative diagnosis, this study confirmed the stem line genotype that is common over an entire tumor as well as in a single biopsy specimen. Biopsy specimens were obtained from 91 gastric carcinoma patients and examined for their microsatellite genotypes using a panel of 41 microsatellite markers on 8 cancer-associated chromosomes. The genotype of the biopsy specimens was compared with that of a surgical specimen, which had been multifocally examined for its intratumoral heterogeneity. Of the 91 pairs of biopsy and surgical specimens, 87 (96%) containing either the same (60 cases) or a similar (17 cases) number of chromosomal losses were categorized into the same microsatellite genotype, and the remaining 4 pairs (4%) were classified into a different genotype. The surgical specimens showed that an extraserosal invasion and lymph node metastasis are frequently associated with either a high-level (4 or more) of chromosomal losses irrespective of the tumor size (73% and 85%) or the large carcinomas > 5 cm in diameter irrespective of the tumor genotype (76% and 83%). The status of the extraserosal invasion and lymph node metastasis (0.691 and 0.802 receiver operating characteristic areas, respectively) predicted by the biopsy genotype and the tumor size corresponded closely to the surgical pathology results. Therefore, the extent of chromosomal losses and the presence of an MSI determined on a biopsy specimen will provide valuable information for making a preoperative genetic diagnosis of a gastric carcinoma.

Genetic classification of intestinal-type and diffuse-type gastric cancers based on chromosomal loss and microsatellite instability

The stage of gastrointestinal cancers has been correlated with the loss of heterozygosity (LOH) and the presence of microsatellite instability (MSI). This study delineated the category of the extent of LOH and the presence of MSI for the genetic classification of the intestinal-type and diffuse-type gastric cancers that frequently exhibited intralesional heterogeneity. A total of 390 tumor foci from 116 gastric cancers were screened using a panel of 40 microsatellite markers on chromosomes 3p, 4p, 5q, 8p, 9p, 13q, 17p, and 18q. One MSI-positive gastric cancer accompanying a LOH-positive focus and 19 gastric cancers with an intralesional LOH heterogeneity with a similar extent were identified. One hundred and sixteen gastric cancers were categorized based on the presence of MSI (16 cases) and the extent of LOH (100 cases) in a representative focus. A large fraction of MSI-positive cases was found in the intestinal-type (94%), late-onset (mean age 68 years), early-stage (75%) diseases (P<0.05). The diffuse-type gastric cancers with a baseline-level loss involving zero or one chromosome showed a correlation with the earlier onset (mean age 45 years), advanced-stage (81%) diseases (P<0.0001). In both the intestinal-type and diffuse-type gastric cancers, a low-level loss involving 0-3 chromosomes (2-3 chromosomes in the diffuse type) and a high-level loss involving 4-7 chromosomes were predominant in the early (69%) and advanced (86%) stages, respectively (P<0.0001), at similar mean ages of onset (61 years and 65 years). Gastric cancers were categorized into low-risk (MSI and low-level LOH) and high-risk (baseline-level and high-level LOH) genotypes displaying cell-type- and age-dependent oncogenicity.

Genetic alterations in poorly differentiated endocrine carcinomas of the gastrointestinal tract

BACKGROUND

The molecular pathogenesis of poorly differentiated endocrine carcinomas of the gastrointestinal tract (GI PDECs) remains unclear. It has been suggested that these lesions either originate from multipotent stem cells that also can serve as the origin of nonendocrine adenocarcinomas or arise due to the dedifferentiation of well-differentiated endocrine carcinomas (WDECs).

METHODS

Ten gastric and 9 colorectal PDECs, 9 gastric WDECs, and 12 colorectal carcinomas (CRCs) were analyzed for loss of heterozygosity (LOH) at 11q13 (MEN1), 17p13.1 (p53), 3p14.2 (FHIT), 3p21.3 (RASSF1A), and 18q23 (DCC/DPC4/Smad2), and for immunohistochemical expression of p53, FHIT, Rb, and p16.

RESULTS

PDECs exhibited high fractional allelic loss (FAL; 0.49), with frequent (> 40%) alterations in p53, Rb, MEN1, FHIT, and 18q. No significant differences were found between gastric and colorectal PDECs. Gastric WDECs also exhibited high FAL (0.44), with frequent alterations in Rb and/or p16, MEN1, and 3p21. CRCs exhibited a low level of FAL (0.23), with frequent (> 50%) p16 and p53 alterations. When gastric PDECs and WDECs were compared, substantial similarities were found with respect to FAL (0.42 vs. 0.44) and with respect to individual gene alterations, except in p53, which was consistently altered only in PDECs. CRCs, which were characterized by a lower FAL (0.56 vs. 0.23) and which lacked alterations in both 3p and Rb, were found to be significantly different from colorectal PDECs.

CONCLUSIONS

GI PDECs demonstrated a high level of chromosomal instability; consistent inactivation of both the p53 and p16/Rb pathways; and frequent LOH at 3p (possibly involving FHIT), the MEN1 locus, and 18q. The profile of genetic alterations in PDECs was more consistent with the profile in WDECs than with the profile in CRCs.

Microallelotyping defines the monoclonal or the polyclonal origin of mixed and collision endocrine-exocrine tumors of the gut

Mixed endocrine-exocrine tumors of the gut are a heterogeneous group of neoplasms with uncertain histogenesis showing different morphologic and clinical features. The aim of this work is to clarify the histogenesis of these tumors by studying the genetic profile of both the endocrine and exocrine components. We performed an allelotyping analysis of five mixed endocrine-exocrine tumors (two gastric and three colonic) and one rectal collision tumor, using 35 polymorphic microsatellite markers covering a total of six chromosomes, including 3, 5q, 6, 11, 17, and 18. The loss of heterozygosity (LOH) analysis showed concurrent losses of the same allele in both the endocrine and exocrine components in all of the five mixed tumors composed by a poorly differentiated endocrine carcinoma or a well differentiated endocrine carcinoma associated with adenocarcinoma or adenoma. Among these tumors an identical LOH pattern was frequently found on chromosomes 17p, 18q, and 5q. Additional allelic losses restricted to the poorly differentiated endocrine carcinoma were often observed. On the contrary, in the only collision tumor composed by a well differentiated endocrine carcinoma associated with adenocarcinoma, completely different allelotypes between the two components were detected. These findings confirm a close genetic relationship between the two distinct histologic components within mixed endocrine-exocrine tumors, supporting the hypothesis that a monoclonal mechanism of tumorigenesis is the most frequent genetic event in mixed exocrine-endocrine tumors. The clonal divergence observed in the only collision tumor, composed by a well differentiated endocrine carcinoma associated with an adenocarcinoma, confirms the existence of double tumors growing next to each other coincidentally but showing different histogenesis and different tumorigenetic pathways.

Neuro-endocrine neoplasms as a result of gene desuppression rather than of a specific cell type of origin

Neuroendocrine differentiation more closely approximates a process of acquisition of features that ambiguously recapitulate certain cellular biologic properties that transgress normal lines of differentiation as these are generally recognized. In fact, it might be more realistic to consider neuroendocrine tumors the result of a process of progressive desuppression via pathways of altered gene expression that would perhaps reflect basic and dynamic aspects of neoplastic transformation and progression in general. In a final analysis, the character and degree of differentiation of a neoplasm might actually often constitute an anomalous combination of features outside the range of normal differentiation pathways and more an expression of an assorted mixture of partially suppressed or desuppressed gene expression profiles as these affect neoplastic cell pathobiology.

Mixed ductal-endocrine carcinomas of the pancreas and ductal adenocarcinomas with scattered endocrine cells: characterization of the endocrine cells

We compared the histological and immunohistochemical features of mixed ductal-endocrine carcinomas of the pancreas with those of ductal adenocarcinomas (DACs) containing scattered tumor-associated endocrine cells (SECs). Three pancreatic neoplasms fulfilled the WHO criteria for mixed ductal-endocrine carcinomas. Two of them showed moderately to poorly differentiated glandular structures composed of both mucin producing and neuroendocrine cells. The third mixed ductal-endocrine carcinoma was of the composite type showing DAC structures and a solid component with small epithelial cells, most of them of neuroendocrine nature. In 32 of 34 cases of DAC located in the head (30 cases) and body to tail (4 cases) of the pancreas and showing lymph-node metastases, SECs were found, but they were few in number and irregularly distributed in the tumors. In three DACs a few SECs were also detected in lymph-node metastases. Double staining for chromogranin A and the proliferation marker Ki-S5 revealed that all SECs that were not intimately integrated into the neoplastic glandular epithelium failed to show proliferative activity and changes of the expression of tumor suppressor genes (p53 and DPC 4). These findings suggest that only those SECs that belong to the proliferative cell fraction may be of neoplastic origin, while the majority of SECs probably constitute a tumor-associated but non-neoplastic cell population. These features contrast with those of mixed ductal-endocrine carcinomas, in which all endocrine cells are a component of the neoplasm.