Testicular lymphoma was first reported by Malassez and Curling in 1866. Primary testicular lymphoma constitutes only 1-7% of all testicular neoplasms and less than 1% of all non Hodgkin lymphoma. We report the case of a 47-year-old man without a particular past medical history, who presented with a painful left testicular swelling that he has noticed for several weeks. Radiological findings consisted in multiple hypoechoic masses that corresponded in histological examination to a diffuse intratubular lymphomatous infiltration situated away from the spermatic cord, the epididymis, ductuli efferentes and rete testis. Immunohistochemical study showed positivity of MUM-1, Bcl-2 and B-cell marker (CD20) and TdT, CD 3, CD5, Bcl-1, CD10, Bcl-6 and Myeloperoksidaz were negative. Ki-67 proliferation index was 90% of neoplastic lenfoid infiltration. The patient underwent full staging for lymphoma by positron emission tomography, showing right superior paratrakeal, precarinal, subcarinal, left paraaortic and retrocrural and left iliac involvement lymph nodes also the right testis and of extra-testicular involvement by the skeleton sistem. The diagnosis of stage III primary testicular large B-cell lymphoma of germinal center B-cell-like group was made. The patient is now treated by chemotherapy. Primary testicular lymphoma is a rare tumor whose diagnosis is based on histological findings. There are non consensual etiological or predisposing factors. Treatment modalities consist in surgical excision, chemotherapy and radiation therapy but the accurate procedures are not standardized. Factors that have been linked to more favorable outcomes include younger patient age, localized disease, presence of sclerosis at pathologic analysis, smaller tumor size, lower histological tumor grade and lack of epididymal or spermatic cord involvement.