Amyloidoma of bone, a plasma cell/plasmacytoid neoplasm. Report of three cases and review of the literature.

Tumoral amyloidosis (amyloidoma) of bone is a rare condition characterized by the massive destructive deposition of AL amyloid in bones. We report three cases. The patients ranged in age from 45 to 78 years and had tumors located in the lumbar spine, scapula, and humeral head measuring 6.5 to 18 cm. The radiologic diagnosis was chondrosarcoma in two cases. Microscopically, there were large, rounded deposits of amorphous eosinophilic material surrounded by numerous giant cells and a sparse lymphoplasmacytic infiltrate. The deposits proved to be composed of AL amyloid showing potassium permanganate resistant congophilia. Immunohistochemistry showed immunoglobulin IgG lambda, IgG kappa, and IgM lambda monoclonality of the plasma cell and (in one case) lymphoid infiltrate. The tumors were classified by morphology and immunohistochemistry as solitary plasmacytomas of bone (two cases) and plasmacytoid lymphoma (one case). During the relatively short follow-up period, one patient progressed to symptomatic generalized amyloidosis and died, one patient died of recurrent tumor, and one patient is alive with no evidence of disease. An extensive review of the world literature showed 34 well-documented similar cases, occurring most often in the spine and skull, causing neurologic symptoms, tending to occur in middle-aged men and frequently progressing to generalized disease. Most if not all AL amyloidomas of bone represent solitary plasmacytomas of bone or plasmacytoid lymphomas.