Plasma Cell Infiltration of the Kidney as a Manifestation of Myeloma: A Report of Three Cases.

Infiltration of renal parenchyma by neoplastic plasma cells in myeloma patients is an unusual finding. We report 3 cases of myeloma, with renal biopsy being the first clue to the diagnosis in one. The plasma cell infiltrate in other two cases was not so evident but immunofluorescence (IF) and immunohistochemical (IHC) stains for light chains helped establish the monoclonal nature of the infiltrate. We surmise that plasma cell infiltration in the kidney can be an important clue to the diagnosis of an underlying myeloma and could in future be regarded as a myeloma-defining event (MDE) if monoclonality is confirmed. This finding could directly affect the prognosis and be a direct indicator of the tumor burden. Further studies are however required to determine the exact prognostic value and precise relationship of such a finding with deranged renal functions in myeloma.