Myeloma cast nephropathy: immunohistochemical and lectin studies.

: Renal disease is a common cause of morbidity and mortality in patients with plasma cell dyscrasia (PCD). We have conducted a systematic study of the formalin-fixed, paraffin-embedded renal tissues from 53 patients with plasma cell dyscrasia, 24 of whom had Bence Jones cast nephropathy (with large casts, often associated with giant cells and polymorphonuclear leukocytes). A battery of 5 immunocytochemical and lectin markers for various segments of the nephron was used [Tetragonolobus lotus, Arachis hypogaea (AH), Tamm-Horsfall protein (THP), epithelial membrane antigen (EMA), and cytokeratin (AE1/AE3)]. In particular, we sought to determine the nature of the intratubular multinucleated giant cells in Bence Jones myeloma cast nephropathy with a variety of epithelial and hematopoietic cell markers. Although tubular epithelial cells stain with their respective markers (whether inflamed, thinned, detached, or adjacent to and lining casts), true intratubular giant cells in PCD were never positive for these tubular markers. In approximately one-third of the cases studied, intratubular and extratubular giant cells stained for several of the seven hematopoietic cell markers employed [i.e., alpha 1-antitrypsin (A1AT), alpha 1-antichymotrypsin (A1ACT), vimentin, and lysozyme], suggesting that giant cells are of hematopoietic origin. The majority of the casts are present in the distal nephron, although some casts were noted in more proximal sites of the nephron. Some larger casts did not stain for THP; smaller casts often showed lamination or stratification of THP staining. Finally, in one-half of the cases, Tamm Horsfall protein (THP) and other distal tubular markers (AH, EMA, AE1/AE3) were found in Bowman's space, almost always in association with interstitial deposits of THP; these markers were virtually never noted in Bowman's spaces of PCD patients without numerous large casts. This suggests that there are communications between distal and proximal nephron, most likely by intraluminal reflux but possibly also through breaks in the tubules and via the interstitium.