Plasma cell leukemia. A report on 11 patients and review of the literature.

OBJECTIVE

Plasma-cell leukemia (PCL) is considered the leukemic variant of multiple myeloma. The diagnosis is based on plasmocytosis exceeding 2,000/mm3 and any evidence of clonal plasma cell proliferation. There are two forms of PCL: the primary form occurring in patients without preceding multiple myeloma or monoclonal gammopathy of undetermined significance, and the secondary form arising as a late manifestation in patients with multiple myeloma. Aim of the study was to describe our series of PCL and to report the main clinical and laboratory findings from the largest series in the literature.

METHODS

Review of all cases of PCL observed from 1976 to 1994 in our Medical Divisions. Med-line research of the largest (more than 5 cases reports) series of PCL from 1969 to 1994.

RESULTS

Eleven cases of PCL were identified. We diagnosed 6 cases with primary PCL out of a total of 512 patients with monoclonal gammopathy (incidence, 1.2%), 4 cases of secondary PCL as terminal phase out of 220 patients with multiple myeloma (incidence, 1.8%), and 1 case of secondary PCL as evolution of monoclonal gammopathy of undertermined significance out of 226 cases (incidence, 0.4%). From our and literature review, that identified 203 cases of primary PCL and 157 cases of secondary PCL, the clinical and the laboratory features did not significantly differ between primary and secondary forms of PCL, whereas significant differences exist between the two forms regarding response to therapy and median survival. In our series, the mean survival was 14 months for primary PCL and 6.8 months for secondary PCL. Two of the 6 patients with primary PCL obtained a complete remission, with a duration of 28 and 23 months, respectively; only 1 patient with secondary PCL had a response to chemotherapy, with a remission of 6 months.

CONCLUSION

Our observation and literature data indicate that PCL, both primary and secondary, is a very poor prognosis disease, that the response rate is higher with combination chemotherapy than single agents, and that primary PCL has a relatively better survival, since secondary plasma PCL usually shows resistance to any type of chemotherapy.