Objective To investigate the expression of PTEN and Caspase-3 in malignant lymphoma of the stomach and explore their role in progression of primary gastric malignant lymphoma. Methods Formalin-fixed paraffin embedded tissues from 56 cases of primary gastric malignant lymphoma and their adjacent non-tumor mucosa were evaluated for PTEN and Caspase-3 protein ex-pression by streptavidin-biotin-complex (SABC) immunohistochemistry. Their expression was compared with clinical tumor parameters with the relationship between PTEN and Caspase-3 expression concerned as well. Results The positive rate of PTEN expression in primary gastric lymphomas(50.0%, 28/56) was significantly lower than that in adjacent non-tumor gastric mucosa(96.4%, 27/28)(P < 0.05). Meanwhile,43 of 56(76.8%)gastric lymphomas indicated Caspase-3 expression, less than that in adjacent non-tumor mucosa (93.5%, 29/31) (P < 0.05). The expression of PTEN was negatively correlated with invasion and lymph node metastasis of gastric lymphoma(P < 0.05), while the Caspase-3 expression was negatively associated with the latter one(P < 0.05). Additionally, the PTEN expression was posi-tively correlated with Caspase-3 expression in the primary gastric malignant lymphoma(P < 0.05). Conclusions The down-regulated expression of PTEN and Caspase-3 played an important role in progression of primary malignant gastric lymphoma. PTEN, as a molecular marker of pathobiological behaviors of tumor, contributes to tumor progression by increasing cell mobility and angiogenesis, as well as decreasing cell adhesion and apoptosis. Objective To investigate the expression of PTEN and Caspase-3 in malignant lymphoma of the stomach and explore their role in progression of primary gastric malignant lymphoma. Methods Formalin-fixed paraffin embedded tissues from 56 cases of primary gastric malignant lymphoma and their adjacent non-tumor mucosa were evaluated for PTEN and Caspase-3 protein ex-pression by streptavidin-biotin-complex (SABC) immunohistochemistry. Their expression was compared with clinical tumor parameters with the relationship between PTEN and Caspase-3 expression concerned as well. Results The positive rate of PTEN expression in primary gastric lymphomas (50.0%, 28/56) was significantly lower than that of adjacent non-tumor gastric mucosa (96.4%, 27/28) (P <0.05) gastric lymphomas indicated Caspase-3 expression, less than that of adjacent non-tumor mucosa (93.5%, 29/31) (P <0.05). The expression of PTEN was negatively correlated with invasion and lymph node metastasis of gastri while the Caspase-3 expression was negatively associated with the latter one (P <0.05). Additionally, the PTEN expression was posi-tively correlated with Caspase-3 expression in the primary gastric malignant lymphoma (P <0.05). Conclusions The down-regulated expression of PTEN and Caspase-3 played an important role in progression of primary malignant gastric lymphoma. PTEN, as a molecular marker of pathobiological behaviors of tumor, contributes to tumor progression by increasing cell mobility and angiogenesis As well as decreasing cell adhesion and apoptosis.