[Human cytogenetics].

A method has been developed to eliminate melanin pigments from chromosomal plates of uveal melanoma tumors. On preparing the chromosomal plates of tumor masses of posterior uveal melanoma for cytogenetic analysis in intermediate pigmented population, it was found that the melanin pigments obscured the cells and thereby the chromosomes. Thus, cytogenetic analysis could not be carried out. Hence, a method was developed in our laboratory to eliminate these obscuring pigments. Several different attempts were made to eliminate the melanin pigments. Finally, washing the cells with phosphate buffered saline before the harvesting stage served the purpose. After harvesting and preparing the chromosomal plates, the cells were found to be devoid of melanin pigments. The protocol would help researchers trying to carry out cytogenetic analysis on melanoma tumor masses in populations with intermediate to dark pigmentation.

Cytogenetics↗

PubMed2001

Biology and therapy of secondary leukaemias.

Secondary leukaemias are common, accounting for more than 40% of all patients with acute myeloid leukaemia (AML) or myelodysplastic syndrome (MDS). A clinical history of exposure to haematotoxins or radiation is helpful; however, many older patients are diagnosed with leukaemia with no antecedent history of exposure. These patients' disease show a remarkably similar phenotype to classic therapy-related leukaemia. The specific cytogenetic abnormalities common to MDS, alkylating-agent-related AML and poor-prognosis AML (3q-, -5, 5q-, -7, 7q-, +8, +9, 11q-, 12p-, -18, -19,20q-, +21, t(1;7), t(2;11)), probably reflect a common pathogenesis distinct from that of other de novo AMLs, although the pathogenetic pathway has yet to be elucidated. Possibly, tumour suppressor genes are implicated and genomic instability may be a cause of multiple unbalanced chromosomal translocations or deletions. Typically, these patients are either elderly or have a history of exposure to alkylating agents or environmental exposure 5-7 years prior to diagnosis. Another distinct entity affects the mixed lineage leukaemia (MLL) gene located on 11q23. These account for about 3% of patients with therapy-related leukaemia and have a short latency period from exposure, usually to an inhibitor of topoisomerase II. Other therapy-related patients with t(8:21), inv16 or t(15;17) translocations should be treated as any other de novo AML with similar cytogenetics. In summary, the major prognostic factor is related to the pathogenetic mechanisms of the leukaemia. Cytogenetics and molecular features are a better predictor of outcome than patient history. Patients should receive standard induction therapy. However, the long-term outcome is relatively poor; the best results being obtained among patients undergoing allogeneic transplantation.

Cytogenetics↗