Soft tissue lymphoma is a very rare clinical entity with varying presentation characteristics and atypical clinical and imaging features. The present report describes a patient who presented with a painless soft tissue mass on the posterolateral surface of the abdominal wall, simulating a neoplasm of mesenchymal origin. After complete surgical excision, the tumor was diagnosed as a diffuse large B-cell lymphoma. No B-symptoms were present and clinical staging did not reveal other sites of disease (stage I EA). The International Prognostic Index score was equal to 1 and classified the patient to the good risk group. Post-operatively the patient was treated with immuno-chemotherapy consisting of rituximab plus cyclophosphamide, epirubicin, vincristine and prednisolone and is currently free of disease for 10 months. The case is discussed with a brief review of the literature on the diagnosis, treatment and outcome of soft tissue lymphomas.