Chromosomal abnormalities in two cases of plasma cell leukemia

Chromosomal and in vitro culture studies in a case of primary plasma cell leukemia

We present a cytogenetic study of a case of primary plasma cell leukemia (PCL) whose plasma cells were cultured in vitro with different mitogens. Cytogenetic studies demonstrated a reduction of the genome, monosomy of chromosomes 8, 13, and 22 being the most frequent. Neither structural changes nor marker chromosomes were observed. The hypodiploid karyotype was confirmed and confined to the neoplastic clone (lambda positive cells) by the MAC (Morphology, Antibody, Chromosome) method, which allows a simultaneous study of chromosomes, cell morphology, and immunologic phenotype. Stimulating the culture of plasmocytes in vitro with IL-6 + PHA, only normal metaphases could be obtained; on the other hand, a large number of abnormal metaphases were observed with the use of LPS as a mitogen. A surprisingly high yield of metaphases was obtained in this case, contrary to the rule in the in vitro growth of plasmocytic proliferations. Possible explanations of this fact are considered.

Chromosome studies in plasma cell leukemia and multiple myeloma in transformation

Four patients with plasma cell leukemia (PCL) and two with multiple myeloma (MM) in transformation had complex numerical and structural chromosome abnormalities. From data published in the literature, the cytogenetic patterns of 46 cases of PCL or MM in the leukemic phase are compared with chromosomal abnormalities found in MM. Although the spectrum of chromosomal abnormalities is comparable in both diseases, the incidence of chromosome abnormalities is higher in PCL than in MM. Hypodiploidy with monosomies for chromosomes 13, 16, 17, and 18 is also more frequent in PCL than in MM. A mutation within the TP53 gene was detected in one of the three patients studied molecularly.

Similar cytogenetic abnormalities in two cases of plasma cell leukemia

Plasma cell leukemia (PCL) is a very rare disease. We report two cases of PCL with complex chromosomal abnormalities: long arm trisomy and short arm partial monosomy of chromosome 1, a marker derived from chromosome 8, and monosomy 13 were found in both cases; other additional chromosome abnormalities were also present in each case. Bastard et al. reports two similar cases in this issue. Cytogenetic studies in PCL have seldom been reported in the literature: chromosomal abnormalities are most often complex: chromosomes 1, 8, 11, 13, and 14 are those most frequently involved. Such cytogenetic findings are observed in advanced multiple myeloma. Cytogenetic, clinical, and immunological findings observed in PCL and the advanced stage of multiple myeloma are arguments for the single origin of pathogenesis.