Primary malignant lymphomas in the female genital tract are rare. Most cases are non-Hodgkin lymphomas of which diffuse large B-cell lymphomas are most commonly seen. Symptoms are associated with other, more common diseases; therefore, a doctors’ delay can be expected. In this case a woman presented with complaints of urinary obstruction due to a large tumour in the pelvic area. A laparotomy was performed. A very large tumour of the uterus was found with adherence to the pelvic wall and urinary bladder. Diagnostic histological examination showed a diffuse large B-cell lymphoma. Treatment with R-CHOP chemotherapy was started shortly after the operation. The treatment of patients with a primary malignant lymphoma of the uterus should be individualized with the following options: surgery, radiotherapy and/or chemotherapy.