Gastric cancer represents the fifth most common malignancy and third most common cause of cancer deaths worldwide. There are two major types of gastric carcinoma: enteric type and diffuse type. Diffuse type gastric cancer is frequently associated with the mutations in E-cadherin coding gene CDH1. In cases of CDH1 mutations complete gastrectomy is indicated. CDH1 mutations are reflected with CDH1 protein loss by immunohistochemistry. The relationship between CDH1 mutations and other markers of tumour aggressiveness, such as tumour proliferation index and the presence of p53 mutations and Her2 amplification is not well studied. Therefore, the aim of our study was to analyse the correlation between CDH1 loss and the expression of Ki67 proliferation marker, mutant oncoprotein p53 and Her2. Standard immunohistochemistry was used to detect the following antigens: CDH1 (MCH-38, Invitrogen), Ki67 (EP5, Bio SB), p53 (DO-7, Leica) and Her2 (EP3, Bio SB). The study results showed that CDH1 mutations, reflected with CDH1 protein loss by immunohistochemistry are detected in 40% of diffuse gastric carcinomas, whilst it is not detected in enteric type gastric carcinomas. Diffuse gastric carcinomas with CDH1 mutations are characterised with more aggressive phenotype, particularly with the presence of higher Ki67 labelling index, p53 mutations and the presence of Her2 positivity. In cases of histological diagnosis of diffuse gastric carcinoma CDH1 testing is recommended.