Objective: To investigate the clinicopathology and DNA ploidy of gastric mucosa associated lymphoid tissue (MALT) lymphoma infiltraving the leiomyomas of the uterus of a patient. Methods: The routine paraffin slides were cut, stained with HE, immunochemically by ABC methodusing the and stained by Feulgen method.Then the DNA ploidy of tumor cells was measured with an image cytometer. Results: In the mucosa, submucosa and the smooth muscle layer of the stomach and in the leiomyomas of the uterus there was diffusive and dense infiltration of centrocyte-like cells. The DNA measurement results were that the distribution of DNA mass of lymphoma cells in stomach and in lymph nodes had a single main aneuploidy peak each, and the distribution of DNA mass of lymphoma cells in leiomyomas of uterus had two peaks; one of them was the diploid, the other aneuploid. Conclusion: The MALT lymphoma cell invasion in uterus must be differentiated with a primary lymphoma in the uterus, the chronic lymphocyte leukemia in uterus and an endometrial stromal sarcoma. The present prognosis of the patient under discussion was poor. The follow-up results indicated the DNA index seemed to be important for predicting the malignancy degree and prognosis.