Two cases of simultaneous occurrence of oncocytoma (OC) associated with small B-cell lymphoma in the same kidney were investigated. Computed tomography, performed for staging purposes, incidentally revealed a small hypo- and hyperattenuating renal mass. Diagnosis of OC was performed on the specimen by morphology, immunohistochemistry and electron microscopy. The patients are in complete remission after a vaccinotherapy with follicular dendritic cells. The occurrence of OC and non-Hodgkin lymphoma in the same kidney has never been reported. These case reports outline that computerized tomography is a sensitive method in the staging of lymphoma. However, when some solid, small hyper- or hypoattenuating masses occur in the kidney, the diagnosis by computed tomography alone is always a challenge and other malignant neoplasms may be considered. Immunohistochemistry and electron microscopy allow a definitive diagnosis of OC.
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