Ploidy and proliferative activity of human gastric carcinoma: a cytofluorometric study on fresh and on paraffin embedded material

Flow cytometric DNA analysis was performed on both fresh and on paraffin embedded samples obtained by gastroscopic biopsies in 5 patients with histologically normal gastric mucosa (20 specimens) and by radical gastrectomies in 9 cases of human gastric cancer (36 specimens). Ploidy and the distribution of cells in the different cell cycle phases were estimated. Results from fresh tissue were compared with those from paraffin embedded material. All the samples of normal mucosa showed a diploid modal DNA content. Unimodal DNA distribution was found both in fresh and paraffin embedded material of 3 well differentiated gastric adenocarcinomas, whereas the remaining 6 tumors (1 moderately differentiated, 4 poorly differentiated and 1 undifferentiated adenocarcinomas) showed aneuploidy. The percentage of cells in S phase in normal tissue and in tumors were respectively 9.0% and 11.9% in the fresh material, and 10.0% and 15.0% in the paraffin embedded material. No statistically significant differences were found between fresh and paraffin embedded samples, whereas the proliferative activity was, in both cases, statistically higher in tumors than in normal mucosa (p less than .01 and p less than .001 respectively). The quality of DNA flow cytometry from paraffin embedded material was comparable with that from fresh samples.     

Comparison of the intratumor DNA ploidy distribution pattern between differentiated and undifferentiated gastric carcinoma

OBJECTIVE: To compare the differences in intratumor DNA ploidy distribution pattern between differentiated and undifferentiated carcinoma of the stomach. STUDY DESIGN: Two hundred five cases of surgically resected gastric carcinoma were studied, comprising 125 differentiated and 80 undifferentiated carcinomas. DNA ploidy was determined by means of flow cytometry in stepwise sections of the entire tumor. The intratumor DNA ploidy distribution pattern was compared between these two histologic types. RESULTS: Differentiated carcinomas comprised 35 cases of predominantly diploid (28%) and 90 cases of predominantly aneuploid (72%) tumors, while undifferentiated carcinomas comprised 46 cases of predominantly diploid (57.5%) and 34 cases of predominantly aneuploid (42.5%) (P < .01). The frequency of cases showing predominantly aneuploidy among the differentiated carcinomas was significantly higher than among the undifferentiated carcinomas at stages IA and IIIA. The rate of cases showing heterogeneity was lower among the early-stage cases than among the advanced-stage cases in both histologic types. Among the differentiated carcinomas, there were 22 cases that had more than six DNA stemlines in each tumor, whereas among undifferentiated carcinomas, there were six such cases (P < .05). CONCLUSION: There were more cases with high malignant potential among the differentiated carcinoma cases than among the undifferentiated carcinoma cases in the present series.     

DNA ploidy pattern and amplification of ERBB and ERBB2 genes in human gastric carcinomas

The DNA ploidy pattern and amplification of ERBB and ERBB2 genes were examined in paraffin-embedded tissue from gastric carcinomas using flow cytometry and a slot-blot hybridization technique. The incidence of aneuploidy in well differentiated adenocarcinomas (56%) was significantly higher (p less than 0.05) than that in poorly differentiated adenocarcinomas (21%). The DNA ploidy pattern was not remarkably different between the primary tumors and metastatic deposits in lymph nodes. Of the nine specimens having an aneuploid stem cell line in the primary tumor and/or in metastases, three showed ERBB2 gene amplification and one showed ERBB gene amplification. The incidence of epidermal growth factor (EGF) immunoreactivity in tumor cells showed no difference between diploid and aneuploid tumors. These findings indicate that aneuploidy is frequently associated with amplification of ERBB and ERBB2 genes.     

DNA ploidy pattern and amplification of ERBB and ERBB2 genes in human gastric carcinomas

The DNA ploidy pattern and amplification of ERBB and ERBB2 genes were examined in paraffinembedded tissue from gastric carcinomas using flow cytometry and a slot-blot hybridization technique. The incidence of aneuploidy in well differentiated adenocarcinomas (56%) was significantly higher (p<0.05) than that in poorly differentiated adenocarcinomas (21%). The DNA ploidy pattern was not remarkably different between the primary tumors and metastatic deposits in lymph nodes. Of the nine specimens having an aneuploid stem cell line in the primary tumor and/or in metastases, three showed ERBB2 gene amplification and one showed ERBB gene amplification. The incidence of epidermal growth factor (EGF) immunoreactivity in tumor cells showed no difference between diploid and aneuploid tumors. These findings indicate that aneuploidy is frequently associated with amplification of ERBB and ERBB2 genes.     

Flow cytometric study of DNA distribution in cytopunctures of benign and malignant breast lesions

One hundred seventy-eight cytopunctures of mammary lesions were obtained for cytologic diagnosis and flow cytometric (FCM) analysis of the nuclear DNA content. All lesions were excised and evaluated histologically; 106 were carcinomas and 72 were benign lesions. The benign lesions showed a diploid DNA content, with one exception. Among the 106 carcinomas, 35 (33%) were diploid, 14 (13%) were tetraploid and 57 (54%) were aneuploid. For 79 carcinomas, the relationship between ploidy and (1) "T" and "N" of TNM staging, (2) the histologic grading of Scarff, Bloom and Richardson, (3) axillary nodal involvement, (4) the presence of estrogen and progesterone receptors, (5) age and (6) menopausal status was investigated. The percentage of aneuploidy was significantly higher (P less than .05) in grade III tumors as compared to grade I tumors. There was no significant relationship between aneuploidy and the other factors. However, a trend was observed between the lack of steroid receptors and a high probability of the tumor being aneuploid. FCM DNA analysis was also carried out on breast carcinomas obtained at surgery in 40 patients for whom FCM DNA analysis had previously been performed on breast cytopuncture specimens. The FCM DNA analyses were found to be best performed on the samples obtained by cytopuncture, which may increase the yield of tumor cells.     

Flow cytometric analysis of head and neck carcinoma DNA index and S-fraction from paraffin-embedded sections: comparison with malignancy grading

Archival, paraffin-embedded, pathology specimens representing pretreatment tissue biopsies from 73 patients with epidermoid carcinoma of the head and neck were analyzed for DNA Index and %S-phase cells by flow cytometry and were scored for quantitative histomorphology. The DNA fluorescence/light scatter size patterns derived from paraffin-embedded specimens were shown to be essentially the same as those from mechanically disaggregated, ethanol-fixed cells obtained from the same tissue specimen. Patterns ranged from lymphocyte-like to highly abnormal DNA Index cytokinetic patterns. The DNA Index values ranged from 0.70 to 3.50 (median 1.42), with an aneuploidy frequency of 63/73 (86%). DNA distribution %S ranged from 4% to 45% (mean 19), with the microscopic malignancy grading showing broad heterogeneity (mean 2.1, range 1.0-3.0, where 1.0-1.7 = well differentiated, 1.8-2.3 = moderately differentiated, 2.4-3.0 = poorly differentiated). Cross-comparison of these data showed that (1) the tumor %S was dependent on DNA Index (higher %S at higher ploidy), (2) low to high malignancy tumors were randomly distributed between diploid/near diploid tumors and high-degree DNA abnormality tumors, and (3) proliferative activity values broadly overlapped between low to high malignancy scored tumors. However, those carcinomas characterized by high DNA Index (greater than or equal to 1.50) and high %S-phase fractions (greater than or equal to 20) had a five fold higher incidence of high-degree malignancy, invasive tumors than diploid/near diploid (%S less than or equal to 19) tumors.     

Association of elevated protein kinase CK2 activity with aggressive behavior of squamous cell carcinoma of the head and neck.

BACKGROUND: Protein kinase CK2 (also known as casein kinase 2) is a messenger-independent protein serine/threonine kinase ubiquitously distributed in eukaryotes. CK2 has been found to phosphorylate a wide variety of cytosolic and nuclear substrates which are intimately involved in regulation of DNA, RNA, and protein synthesis, and differentiation. We therefore addressed the hypothesis that malignant transformation of upper aerodigestive tract mucosa to squamous cell carcinoma of the head and neck (SCCHN) might be associated with altered CK2 activity. MATERIALS AND METHODS: To this end, we subjected surgical specimens of SCCHN tumors and of normal oropharyngeal mucosa to subcellular fractionation. We then quantitated CK2 activity in cytosol and nuclei of these specimens using a CK2-specific peptide substrate (Arg-Arg-Arg-Glu-Glu-Glu-Thr-Glu-Glu-Glu). RESULTS: We found that CK2 activity was significantly elevated in both nuclear (p < 0.0005) and cytosolic (p < 0.0034) compartments of SCCHN tumors, relative to normal oropharyngeal mucosa. Moreover, CK2 activity in the cellular cytosolic fraction of SCCHN tumors was associated with less differentiated histologic grade (p < 0.037), positive nodal metastatic status (p < 0.056), and a poor clinical outcome (p < 0.028). Kaplan-Meier cumulative survival analysis revealed greatly reduced survival in the high-CK2 activity patient group, with high statistical significance (p < 0.023). CONCLUSIONS: These preliminary data reveal that malignant transformation of the upper aerodigestive tract mucosa is associated with altered CK2 activity. The results further suggest that dysregulation of this protein kinase may play a significant role in the pathobiology of SCCHN, and that CK2 activity may be a prognostic indicator in this malignancy.     

Genetic alterations in gastric precancerous lesions

To investigate the occurrence of 17p (p53) loss of heterozygosity (LOH) and increased 4N or aneuploidy in gastric precancerous lesions (GPL), and their association with Helicobacter pylori (H pylori) infection. A total of 78 gastric mucosal biopsy specimens, including 10 normal mucosa and 68 gastric precancerous lesions [chronic atrophic gastritis (CAG, n = 20), intestinal metaplasia (IM, n = 12), low grade dysplasia (LGD, n = 15), and high grade dysplasia (HGD, n = 21)] were studied using PCR and flow cytometry. A modified Giemsa staining technique was used to detect H pylori. The study was performed in Erzurum Numune Hospital between 2007 and 2009. 17p (p53) LOH was observed in (1/20) 5% of CAG, in (2/12) 16% of IM, in (3/15) 20% of LGD and in (11/21) 53% of HGD. There was correlation between prevalence of 17p (p53) LOH and histological type of GPL (P = 0.004). Similarly, increased 4N or aneuploidy was detected in (1/20) 5% of CAG, in (1/12) 8% of IM, in (2/15) 13% of LGD and in (9/21) 43% of HGD. The correlation was found between aneuploidy and histological type of GPL (P = 0.009). However, there was no correlation between presence of H pylori infection in histological type of GPL (P = 0.921). On the other hand, a significant association was found between increased 4N or aneuploidy and 17p (p53) LOH in all of GPL (P = 0.0001). However, there was no statistically significant association between H pylori infection and 17p (p53) LOH or increased 4N/aneuplody in GPL. 17p (p53) LOH and increased 4N or aneuploidy are closely related to the early stages of gastric carcinogenesis.     

DNA ploidy and immunomarking of bladder urothelial tumors before and after intravesical bacillus Calmette-Guérin treatment

OBJECTIVE: To investigate DNA ploidy and immunoexpression of Ki-67 and p53 as predictivefactors in cases of superficial urothelial cell carcinoma (UCC) treated with bacillus Calmette-Guérin (BCG). STUDY DESIGN: Samples were obtained from 66 patients with UCC (pTa grade 3 or high grade and pT1 independent of grade or with concomitant carcinoma in situ) before and after intravesical BCG treatment. DNA ploidy analysis (ploidy balance, degree of hyperploidy and aneuploidy, proliferation index) was done by static cytometry. Ki-67 and p53 were analyzed immunohistochemically in paraffin-embedded tissue, and their quantification was carried out using an image analysis system. RESULTS: During a mean follow-up of 63.8 months, 31 of the 66 patients developed recurrent tumors (46.9%). DNA ploidy analysis showed that ploidy balance as well as degree of hyperploidy and aneuploidy were not statistically different between recurrent and nonrecurrent tumors. Only proliferation index was statistically significant between recurrent and nonrecurrent tumors. No statistically significant difference was observed in the percentage of Ki-67- and p53-positive cells between primary tumors that recurred and those that did not. CONCLUSION: These findings suggest that only proliferation index has predictive value for recurrence and progression in UCC treated with BCG.     

DNA aneuploidy as a specific marker of neoplastic cells in FNAB of the thyroid

OBJECTIVE: To investigate whether DNA image cytometry (ICM) could be of value in the specific identification of neoplastic cells in cytologic specimens of the thyroid. STUDY DESIGN: FNABs of thyroid from 162 patients with different benign and neoplastic diseases were investigated. Nuclear DNA content in thyroid cells was measured after Feulgen staining using a TV image analysis system. Data were correlated with clinical and histologic patient follow-up. The occurrence of abnormal DNA stemlines was used as a marker for aneuploidy and thus for neoplasia. RESULTS: None of the 89 cases without tumor cells revealed DNA aneuploidy. An abnormal DNA stemline was found in 55% of histologically proven benign thyroid tumors (follicular or oncocytic adenomas) and in 59.5% of malignant tumors. The positive predictive value of DNA aneuploidy in FNABs of the thyroid for neoplasms was 100%. The negative predictive value of DNA nonaneuploidy for the prediction of tumor-free histologic or clinical follow-up was 79.4%. CONCLUSION: DNA image cytometry may be helpful in the specific identification of neoplastic follicular cells. DNA ICM on FNABs of the thyroid is an additional tool to achieve early identification of patients with nodular lesions of the thyroid that have to be operated on. DNA euploidy excludes the presence of neither malignancy nor neoplasia.     

Flow cytometric analysis of DNA aneuploidy in primary and metastatic human solid tumors

DNA histograms were measured by flow cytometry for 656 human solid tumors (365 primary and 291 metastatic). The proportion of aneuploid cells in cell suspensions obtained by mechanical disaggregation was significantly higher than those obtained after enzymatic disaggregation (collagenase + DNAse) of the same tumor. A strong correlation was observed between the values of DNA-indices measured after staining with propidium iodide and with 4',-6-diamidino-2-phenylindole (r = 0.97). Aneuploid cells were observed in 430 tumors (66%); 30 of these had two aneuploid stemlines, and two had three aneuploid stemlines. The overall frequency of aneuploidy was 61% among primary and 71% among metastatic tumors. The median value of the DNA index was 1.67 for 224 primary aneuploid tumors and 1.68 for 206 metastatic aneuploid tumors. For most diseases, the largest proportion of aneuploid primary and metastatic tumors had DNA-indices in the hypertriploid region. No major differences in frequency and degree of aneuploidy was observed between primary and metastatic tumors. For carcinomas of the bladder and prostate, frequency of aneuploidy was higher among poorly differentiated, than among moderately and well-differentiated tumors. For carcinomas of the breast and for sarcomas, tumors with DNA-indices of greater than 2.0 were observed mostly in the poorly differentiated group. For patients with carcinomas of the bladder and prostate most tumors at earlier stages of disease were diploid; whereas most tumors at later stages of disease were aneuploid. For patients with carcinomas of the ovary, colon, and kidney, no relationship between stage of disease and aneuploidy was evident.     

Prognostic significance of DNA ploidy determined by high-resolution flow cytometry in breast carcinoma

OBJECTIVE: To assess the prognostic value of DNA ploidy in breast carcinoma and its relation to other established prognostic factors. STUDY DESIGN: We evaluated DNA ploidy in 303 breast carcinoma patients with a median follow-up of 63 months. Flow cytometry was performed on frozen tumor material, yielding histograms with narrow peaks (median coefficient of variation of 2.08). DNA ploidy pattern was classified as either diploid versus nondiploid, euploid (diploid and tetraploid) versus aneuploid or diploid/near-diploid (DNA index < 1.2) versus other, and correlated with relapse-free (RFS) and cancer-specific survival (CSS) along with tumor size, histologic grade and type, axillary lymph node involvement, menopausal and steroid receptor status, age and type of treatment. RESULTS: Seventy-one percent of tumors were DNA nondiploid (14% tetraploid and 57% aneuploid). There was a strong association between DNA ploidy and histologic grade. Histologic grade, lymph node status, tumor size and DNA ploidy (regardless of the classification used) were all significantly associated with RFS and CSS in multivariate analysis. CONCLUSION: These results suggest that DNA ploidy, at least when determined from frozen tumor tissue, is an independent prognostic factor in breast carcinoma; however, its prognostic power seems to be inferior to that of histologic grade, with which it strongly correlates.     

DNA distribution in non-small-cell lung carcinomas and its relationship to clinical behavior

A study of 187 surgical specimens of tumors of patients with non-small-cell lung carcinomas was carried out by means of flow cytometry. Eighty-four percent of the tumors were classified as tumors with abnormal DNA stemlines (DNA aneuploidy). Patients with tumors demonstrating DNA aneuploidy had significantly shorter survival times than those with tumors demonstrating DNA diploidy (p = .009). Cell cycle analysis was possible in 122 tumors. Patients whose tumors had 0-8% S-phase cells died later than patients whose tumors had 9-16% S-phase cells (p = .018). In addition, patients with tumors with a low fraction of labeled S-phase cells (autoradiography) had a better prognosis than patients with tumors with a high proportion of labeled S-phase cells (p = .041).     

Evaluation of tumor heterogeneity of prostate carcinoma by flow- and image DNA cytometry and histopathological grading.

BACKGROUND: Heterogeneity of prostate carcinoma is one of the reasons for pretreatment underestimation of tumor aggressiveness. We studied tumor heterogeneity and the probability of finding the highest tumor grade and DNA aneuploidy with relation to the number of biopsies. MATERIAL AND METHODS: Specimens simulating core biopsies from five randomly selected tumor areas from each of 16 B?cking's grade II and 23 grade III prostate carcinomas were analyzed for tumor grade and DNA ploidy by flow- and fluorescence image cytometry (FCM, FICM). Cell cycle composition was measured by FCM. RESULTS: By determination of ploidy and cell cycle composition, morphologically defined tumors can further be subdivided. Heterogeneity of tumor grade and DNA ploidy (FCM) was 54% and 50%. Coexistence of diploid tumor cells in aneuploid specimens represents another form of tumor heterogeneity. The proportion of diploid tumor cells decreased significantly with tumor grade and with increase in the fraction of proliferating cell of the aneuploid tumor part. The probability of estimating the highest tumor grade or aneuploidy increased from 40% for one biopsy to 95% for 5 biopsies studied. By combining the tumor grade with DNA ploidy, the probability of detecting a highly aggressive tumor increased from 40% to 70% and 90% for one and two biopsies, respectively. CONCLUSION: Specimens of the size of core biopsies can be used for evaluation of DNA ploidy and cell cycle composition. Underestimation of aggressiveness of prostate carcinoma due to tumor heterogeneity is minimized by simultaneous study of the tumor grade and DNA ploidy more than by increasing the number of biopsies. The biological significance of coexistent diploid tumor cell in aneuploid lesions remains to be evaluated.     

Roles of DNA cytometry and detection of EBERs in predicting a diagnosis of nasopharyngeal carcinoma.

OBJECTIVE: To analyze the suitability of DNA cytometry and detection of Epstein-Barr virus (EBV)-encoded RNAs (EBERs) on nasopharyngeal brushings for predicting a diagnosis of nasopharyngeal carcinoma (NPC). STUDY DESIGN: Cytologic preparations in 66 cases suspicious for NPC were evaluated for NPC diagnosis in comparison with the histologic diagnosis. Based on cytologic examination, 38 cases containing cytologically proven cancer and 8 cases interpreted as cytologically negative for cancer with adequate cellularity in the smear specimens were analyzed for DNA ploidy with an image analyzer and for EBER expression by in situ hybridization (ISH). RESULTS: Based on the cytologic diagnosis, DNA aneuploidy analysis, DNA nondiploidy analysis and EBER detection demonstrated a sensitivity of 50%, 84% and 92%, respectively, with the same specificity, 100%, for predicting a diagnosis of cancer. Their negative predictive values were 30%, 57% and 73%, respectively. There was a significant difference between DNA aneuploidy analysis and EBER analysis in sensitivity (P < .001) and in negative predictive value (P < .05) but not between DNA nondiploidy analysis and EBER analysis even though EBER analysis showed a slightly higher value in both parameters (P > .1 and P > .5, respectively). CONCLUSION: ISH for EBERs in cytologic smears showed a role superior to that of DNA aneuploidy analysis in the diagnosis of NPC. Considering its advantages of simple experimental conditions and lower cost as compared with DNA measurement, EBER detection can play a practical and important diagnostic role in patients suspected of having primary NPC.     

Dual-parameter flow cytometric analysis coupling the measurements of forward-angle light scatter and DNA content of archival ovarian carcinomas of low malignant potential

Paraffin-embedded archival specimens from 45 cases of ovarian carcinoma of low malignant potential (OCLMP) were analyzed by flow cytometry (FCM) using propidium iodide (PI) staining. Since single-parameter FCM analysis is often deficient in the resolution of subtle near-diploid DNA-aneuploid populations, forward-angle light scatter (FALS) was measured as a second parameter. DNA aneuploidy was identified in 15 cases (33%). In 7 of those 15 cases, aneuploidy was resolved with single-parameter FCM; in the remaining 8 cases, DNA aneuploidy was resolved only following dual-parameter analysis coupling DNA content and FALS. In all 15 cases, a single near-diploid aneuploid population was observed (mean DNA index = 1.2); there were no tetraploid aneuploid cases. The proliferative activity for all 45 cases studied ranged from 1.0% to 8.9%, with a mean of 3.5%. No difference in mean proliferative activity was observed between the aneuploid and diploid tumors (P greater than .05). To exclude the possibility that PI staining artifacts caused the observed aneuploidy, five of the eight cases shown to be aneuploid by dual-parameter analysis were further studied using an alternate DNA-binding dye, DAPI, yielding similar results. To exclude the possibility that contaminating stromal and/or inflammatory cells caused the observed aneuploidy, samples from a subset of the dual-parameter cases were sorted, revealing the aneuploid populations to be composed primarily of tumor nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of DNA aneuploidy, overexpression of p53 gene product, and cellular proliferation in the progression of gastric cancer.

DNA aneuploidy, p53 overexpression, and high cell proliferation frequently occur in gastric cancer. However, little is known about the time of their appearance throughout cancer progression. Therefore, the objective of the present study was to determine when such abnormalities occur during gastric cancer progression. We classified the gastric cancers examined into intestinal (n = 65) and diffuse (n = 34) types. DNA ploidy was examined using flow cytometry and expression of MIB-1 and p53 immunoreactivity were studied using the avidin-biotin complex method in three stages of gastric cancer (mucosal, submucosal, deeply invasive cancer, i.e., advanced cancer). The incidence of DNA aneuploidy in intestinal-type mucosal cancers (15/27, 55.6%) was lower than that of submucosal invasive cancers (14/16, 87.5%) or advanced cancers (19/22, 86.4%), while a low incidence of DNA aneuploidy was observed in each diffuse-type cancer group (mucosal, 1/12, 8.3%; submucosal invasive, 3/9, 33.3%; advanced, 8/14, 57.1%). Although overexpression of the p53 gene in intestinal-type cancer was found in early stage, that in diffuse-type cancer was observed in advanced stage. Among the intestinal-type mucosal cancers, the MIB-1 percent positive was higher in aneuploid tumors than diploid ones. DNA aneuploidy and overexpression of the p53 gene may play an important role in the early tumorigenesis of intestinal-type gastric cancer and in the late event of tumorigenesis of diffuse-type gastric cancer.     

Expression of basic fibroblast growth factor in human gastric carcinomas.

The expression of mRNA for the basic fibroblast growth factor (FGF) gene was examined in seven human gastric carcinoma cell lines and in tissue from 29 gastric carcinomas together with the adjacent normal mucosa. Among the seven gastric carcinoma cell lines, the MKN45 cell line expressed mRNA for the basic FGF gene. Basic FGF protein production was confirmed by flow cytometric analysis and immunohistochemistry. Among the surgical specimens, 16 (55%) of 29 gastric carcinomas showed higher levels of basic FGF mRNA than the normal mucosa. Interestingly, in scirrhous gastric carcinomas characterized by their fibrous stroma and rapid growth, 9 (69%) of 13, samples examined revealed higher levels of basic FGF mRNA than normal mucosa, whereas only 3 (33%) of the 9 well differentiated adenocarcinomas studied produced similar results. Immunohistochemically, basic FGF protein was localized in tumor cells. These results suggest that basic FGF produced by tumor cells may play an important role in producing fibrosis and angiogenesis in gastric carcinomas.     

Genetic and epigenetic alterations of tumor suppressor and tumor-related genes in gastric cancer

Both genetic and epigenetic alterations of tumor suppressor and tumor-related genes involved in the pathogenesis of gastric cancer are reviewed here, and molecular pathways of gastric carcinogenesis are proposed. Gastric carcinomas are believed to evolve from native gastric mucosa or intestinal metaplastic mucosa that undergoes genetic and epigenetic alterations involving either the suppressor pathway (defects in tumor suppressor genes) or mutator pathway (defects in DNA mismatch repair genes). Methylation of E-cadherin in native gastric mucosa results in undifferentiated carcinomas (suppressor pathway), while methylation of hMLHI results in differentiated foveolar-type carcinomas (mutator pathway). The majority of differentiated gastric carcinomas however, arise from intestinal metaplastic mucosa and exhibit structural alterations of tumor suppressor genes, especially p53. They appear to be related to chronic injury, perhaps due to Helicobacter pylori infection. Approximately 20% of differentiated carcinomas (ordinary-type) have evidence of mutator pathway tumorigenesis. Mutations of E-cadherin are mainly involved in the progression of differentiated carcinomas to undifferentiated tumors. The molecular pathways of gastric carcinogenesis depend on the histological background, and gastric carcinomas show distinct biological behaviors as a result of discernible cellular genetic and epigenetic alterations.