INTESTINAL MULTINODULAR A-LAMBDA-AMYLOID DEPOSITION ASSOCIATED WITH EXTRAMEDULLARY PLASMACYTOMA IN 3 DOGS - CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDIES

Intestinal extramedullary plasmacytomas (EMPs) are rare rumours in dog s. Three cases of canine intestinal EMP with amyloid deposits are desc ribed in this report. These rumours, which were located in the rectal submucosa, had variable numbers of well-differentiated plasma cells an d fewer multinucleated giant cells of plasmacytoid and histiocytic mor phology, admired with abundant amyloid. Two cases had metaplastic cart ilage and bone within the amyloid deposits. Immunohistochemically, the plasma cells of all three tumours reacted for lambda-light chains of immunoglobulins but not for kappa-chains, indicating monoclonality. Pl asma cells of two tumours were also positive to CD79a antiserum. Amylo id deposits were labelled with an A lambda (amyloid of immunoglobulin lambda-light chain origin) antiserum but not with antisera against its precursor protein, the immunoglobulin lambda-light chains, indicating possible conformational changes of amyloidogenic proteins during thei r transformation into amyloid. (C) 1998 W.B. Saunders Company Limited.