Long-term study of gammopathies. Clinically benign cases showing transition to malignant plasmacytomas after long periods of observation

Since 1968, our Clinical Chemistry laboratory has been performing protein electrophoresis on sera of patients with total protein levels of over 85.0 g/L and under 55.0 g/L. Monoclonal gammopathies were found in 534 cases. Immunoelectrophoresis was carried out using antisera to the heavy chains gamma, alpha, mu, delta, and epsilon, and to the light chains kappa and lambda. Urine from these patients was tested for Bence-Jones protein. Records and smears, when available, were examined for clinical or hematologic evidence of multiple myeloma and other lymphoid malignancies. Sixty-five percent of these 534 cases were referred to the laboratory with a provisional diagnosis of plasmacytoma but 35% were not clinically suspected. Twenty-two cases with gammopathy, but no clinical or hematologic symptoms of plasma cell dyscrasia, were selected and followed up. Eight of these patients (36%) had converted to malignancy by the end of ten years. These results show the value of screening for abnormal proteins and the need for a long-term follow-up in such patients, prior to diagnosis of plasma cell dyscrasia.