A morphological and immunohistochemical evaluation of gastric carcinoma in the Western Cape province of South Africa

Background: Gastric resections for carcinoma are common, but gastric carcinoma in South Africa, and particularly within the Western Cape province, has not been well documented. Method: The objective of the study was to immunohistochemically evaluate HER2/neu overexpression, determine aberrations in beta-catenin and epithelial-cadherin (E-cadherin) expression, and correlate these findings with gastric carcinoma subtypes. Results: Ninety-seven gastric adenocarcinoma resections were morphologically categorised as intestinal-, diffuse-or mixed-type adenocarcinomas, and immunohistochemically stained for beta-catenin, E-cadherin (extracellular and cytoplasmic domains) and HER2/neu. The results of staining were compared between the subtypes for statistically significant differences. All 97 cases were confirmed as gastric adenocarcinomas, with 39 (40%) intestinal-type, 51 (53%) diffuse-type, and 7 (7%) mixed-type tumours identified. Patient ages ranged from 18-84 years. HER2/neu was overexpressed in 12 (12%) cases, with intestinal-type morphology (p = 0.017) reported in nine. Fourteen cases (14%) demonstrated abnormal beta-catenin localisation. Aberrant E-cadherin (extracellular domain) localisation occurred in 36 (37%) cases. Diffuse-type morphology was associated with a significantly high proportion (p = = 0.001). Aberrant E-cadherin (cytoplasmic domain) localisation occurred in 7 (7%) cases. A significantly high proportion (six of these cases) (p = 0.023) of these was diffuse-type morphology. Eleven (11%) adenocarcinomas occurred in patients aged = 40 years, with intestinal morphology reported in nine of these 11. Aberrant E-cadherin (extracellular domain) localisation was noted in seven of the 11, a significantly high proportion when compared to that in the older patients (p = 0.025). Conclusion: Distinct immunomorphological correlations are apparent in tumours demonstrating HER2/neu overexpression or abnormal E-cadherin localisation. Intestinal morphology, poor differentiation and E-cadherin abnormalities are frequently demonstrated in tumours occurring in younger individuals.