[Perirenal immunoblastic lymphoma. Description of a case]

The primary perirenal localization of non-Hodgkin lymphomas is rare and normal methods of image diagnosis do not enable a reliable preoperative diagnosis. In the majority of cases renal function is not affected and this pathology is often presented as an occasional finding. The pathologies included in the differential diagnosis are renal neoplasias, abscess and inflammatory processes in a perirenal site. Echotomography shows the lesion as an hypoanechoic zone surrounding the kidney. Computed tomography show it as isodense with the renal parenchyma. Histological tests together with immunohistochemical tests identified a malignant large B cell immunoblastic-type lymphoma in the case described here, with plasmoblastic-plasmocytic differentiation and high malignancy according to the Working Formulation. The pathogenesis of this rare localisation is controversial. We maintain that lymphomatous proliferation may be triggered off by lymphatic follicles present in the perirenal space. The concomitant presence of other clinical signs, such as splenomegalia and adenopathies, may contribute to the diagnosis. On the contrary, monolateral involvement in the absence of other signs, as in this case, raises considerable problems of differential diagnosis. Perirenal lymphoma must therefore always be borne in mind in the diagnosis of renal or perirenal masses.