Résumé
Chronic myelogenous leukemia (CML) is a clonal disorder that presents with a stable period followed by an accelarated phase. The most frequent chromosomal abnormality described is t(9;22). Alterations of chromosome 17, where p53 is located, have been described during transformation. We studied a 23-year-old male who presented with chronic myelogenous leukemia. The karyotype demonstrated 46,XY,t(9;22) (q34;qll) in 12 percent of mitoses and hyperdiploidy in 43 percent. Forty six months later the patient suffered a blast crisis characterized by absolute basophilia; the cytogenetic study demonstrated 48,XY,+8,t(9;22(q34;qll), +der(22)t(9;22)(q34;qll),+i(17)(q10) in 18 percent of the mitoses, 46,XY,t(9;22) (q34;qll) in 34 percent and hyperdiploidy in 23 percent. Since there was i(17)(q10) during this stage, a retrospective DNA study of the biopsy material before and after the transformacition was performed. In the chronic phase, p53 was present in normal amounts, during transformation there was loss of genetic material from the p53 region. The protein product of suppressor gene p53 normally works holding the proliferation of cells. When there is the formation of an isochromosome, genetic material is lost; thus, in this patient, p53 was delted upon the observation of i(17). Lastly, this case shows how DNA can be extracted from slides; this technique is novel and can be used for retrospective studies when parafin block or fresh tissue are not available