The most common paraprotein-associated lesions are myeloma cast
nephropathy, monoclonal immunoglobulin deposition disease, and amyloidosis.
5-11) There are some morphologic patterns that are readily recognizable at the light microscopic level, especially when the manifestations are florid, including that of myeloma cast nephropathy, nodular glomerulosclerosis associated with light or heavy chain deposition disease, and light and heavy chain (AL and AH) amyloidosis.
Macrophage origin of the multinucleated cells of myeloma cast nephropathy.
On light microscopy, there was evidence of large eosinophilic hyaline casts with mononuclear cells and multinucleated giant cells, and immunofluorescent microscopy showed positive kappa staining of tubular casts; these findings were consistent with myeloma cast
nephropathy (Figure 1).