EXTENSIVE EXTRAMEDULLARY DISEASE IN MYELOMA - AN UNCOMMON VARIANT WITH FEATURES OF POOR-PROGNOSIS AND DEDIFFERENTIATION

BACKGROUND. The development of extramedullary plasmacytomas and elevat ed serum lactic dehydrogenase (LDH) in myeloma indicates poor prognosi s. A 75-year-old man was diagnosed with immunoglobulin (Ig) A, lambda myeloma when he developed pathologic rib fractures, hypercalcemia, and anemia. After 6 months of treatment with melphalan and prednisone, he was in complete remission as evidenced by the disappearance of the mo noclonal protein in the serum and free light chain in the urine. Eight months after diagnosis, his disease took an unusual course with the s imultaneous development of plasmacytomas in the skin, breast, stomach, and pancreatic head, complicated by severe upper gastrointestinal ble eding and obstructive jaundice. METHODS. Immunohistochemical staining of the marrow and breast mass was done using monoclonal antibodies aga inst B-cell and T-cell antigens as well as kappa and lambda light chai ns. In situ hybridization was performed to detect ras oncogene overexp ression in the breast mass. RESULTS. Immunohistochemical staining of t he original marrow and breast mass was positive for IgA and lambda, co nfirming the identical clonal origin of the plasma cells. The disorder expressed elevated serum LDH, both at diagnosis and relapse. Features of dedifferentiation were expressed by the disappearance of myeloma p rotein in the serum at relapse, absence of marrow plasma cell infiltra tion, and development of multiple extramedullary plasmacytomas. There was no overexpression of H-ras or N-ras oncogenes by in situ hybridiza tion of the plasmacytoma from the breast. The patient died shortly aft er the development of the extramedullary plasmacytomas. CONCLUSIONS. T he simultaneous appearance of plasmacytomas in multiple extramedullary sites heralds a change of clinical behavior in myeloma. When accompan ied by the disappearance of serum myeloma protein, and marrow plasma c ell infiltration, and serum LDR elevation, the disorder may follow a f ulminant course. (C) 1996 American Cancer Society.