We report on a 65-year-old white woman who was hospitalized because of symptoms of an acute adrenocortical insufficiency. A CT scan revealed the presence of a large mass in the left kidney that infiltrated the adrenal gland. Fine needle aspiration cytology of the mass under imaging control failed to achieve a correct diagnosis, and nephrectomy was undertaken with a preoperative diagnosis of renal cell carcinoma. However, the frozen section reveals a neoplasm of large lymphoid cells with a diffuse growth pattern. Immunohistochemistry confirms the B-cell nature of the neoplasm (CD20+). The final diagnosis was non-Hodgkin B-cell high grade centroblastic lymphoma (KIEL classification). Postoperative studies failed to show lymph node or bone marrow infiltration by neoplastic cells. We found reports on only 60 malignant lymphomas, considered to be primary to the kidney. They usually affect middle-aged people, can be diagnosed with imaging techniques, and seem to show a better prognosis than other types of lymphoma.