Sclerosing malignant lymphoma mimicking idiopathic retroperitoneal fibrosis: importance of clonality study  C.S Chim, MD, R Liang, MD, A.C Chan, MD  The American Journal of Medicine  Volume 111, Issue 3, Pages 240-241 (August 2001) DOI: 10.1016/S0002-9343(01)00777-X

Figure 1 A. Diffuse large B-cell lymphoma. There was diffuse infiltration by a monotonous population of large abnormal lymphoid cells, mostly with a centroblastic appearance (hematoxylin and eosin stain, magnification × 500). B. Retroperitoneal biopsy specimen in 1988 showed infiltration by small lymphocytes and occasional polyclonal plasma cells within a markedly sclerosed stroma. In focal areas, the small lymphoid cells formed larger follicular aggregates. The features were suggestive of idiopathic retroperitoneal fibrosis; however, with hindsight, some of the small lymphoid cells showed slight nuclear irregularity in keeping with a low grade B-cell lymphoma (hematoxylin and eosin stain, magnification × 250). C. Polymerase chain reaction testing for immunoglobulin H (IgH) gene rearrangement showing clonal IgH rearrangement. Lanes: M = molecular weight marker; P = positive control from a patient with B-cell lymphoma; S = DNA from the 1988 retroperitoneal biopsy specimen of this patient. Lanes 1 to 4 = negative control patients with deep vein thrombosis showing absence of clonal IgH rearrangement; B = reagent blank, as negative control. The American Journal of Medicine 2001 111, 240-241DOI: (10.1016/S0002-9343(01)00777-X)