Cytogenetics of acutely transformed chronic myeloproliferative syndromes without a Philadelphia chromosome. A multicenter study of 55 patients. Groupe Français de Cytogénétique Hématologique.

In a multicenter study by the Groupe Français de Cytogénétique Hématologique, chromosome investigation was undertaken in 55 cases of acutely transformed Philadelphia-negative chronic myeloproliferative syndromes (polycythemia vera, 34 cases; essential thrombocythemia, two cases; myelofibrosis with myeloid metaplasia of the spleen, 12 cases; other, unclassified myeloproliferative disorders, seven cases). Thirty-seven patients had received 32P radiotherapy and/or alkylating agents during the chronic phase, eight had received other cytotoxic drugs, and ten had received a noncytotoxic treatment. The duration of chronic phase ranged from 1 to 29 years (mean, 9.2 years). Nineteen karyotypes were established at the onset of transformation, when the percentage of bone marrow blasts was still low; 31 were performed at an overt acute leukemia stage, and five were carried out at both stages. Clonal abnormalities were seen in 96.3% of the karyotypes, of which 80.0% were structural defects, 20.0% hypoploidies, 36.4% hyperploidies, and 36.4% complex karyotypes or karyotypes with variations. In 20 cases the chromosome changes were of the type usually found in secondary leukemias; however, no clear relationship could be established between chromosomal defects and chronic phase treatments. The most frequently involved chromosomes were: #1 in 11 cases, #5 in 13, #6 in 13, #7 in 13, #8 in six, #12 in seven, #13 in 12, #17 in 14, #20 in seven, and #21 in four. Simple karyotypes, partial trisomy 1(q), del(6p), +8, +9, der(12q), del(13q), i(17q), and del(20q) are probably related to the disease, whereas, complex karyotypes, -5, del(5q), -7, del(7q), -17, and der(17) [other than an i(17q)] probably reflect treatment-induced events.