[Clinical course and phenotypic instability in 4 cases of multiple myeloma: a biological model of tumors].

Four cases of multiple myeloma (MM) are reported in which the coexistence and/or the alternance of different plasma cell clones were observed. Genetic instability is typical of all tumors but in MM it is particularly striking due to the M component marker. In this respect, malignancies reveal the presence of an unremitting competition of different cell populations for the phenotype prevalence. When this phenomenon is related to the clinical picture it is possible, as in our cases, to ascertain that the appearance of new clones often corresponds to significant changes in the disease evolution.