Fig. 1

Renal biopsy and ascitic fluid findings

(A–C) On IF, coarse, granular, predominantly capillary wall deposits are noted during IgG 3(2+) (Magnification, × 400) and lambda (2+) staining while negative for kappa staining (Magnification, both×100). (D) The membranoproliferative pattern of glomerular injury with lobular accentuation, mesangial matrix expansion, and hypercellularity, and occasional acellular mesangial nodule (Periodic acid–Schiff, magnification, ×400). (E) Broad and elongated subendothelial immune complex deposits and collagen fibers in the mesangium are observed (Masson’s Trichrome Staining, magnification, ×400). (F) Transmission electron microscopy image shows numerous subendothelial electron-dense deposits (Magnification, ×5000). (G) Immunohistochemical analysis of the ascitic fluid shows tumor cells with a strong expression of MUM-1(Magnification, ×100). (H) The tumor cells are strongly immunopositive for CD138 (Magnification, × 200). (I) Hematoxylin and eosin staining of the ascitic fluid reveals abundant plasmablast-like lymphocytes, presenting as round or oval-shaped cells with eccentrically located nuclei and distinct single or multiple nucleoli (Magnification, × 100)