Characterisation of TP53 abnormalities in chronic lymphocytic leukaemia.

Abnormalities of TP53 in chronic lymphocytic leukaemia (CLL) correlate with aggressive disease and transformation. We studied 115 patients with CLL including 90 untreated, 25 with heavily pretreated/refractory CLL using fluorescent in situ hybridisation (FISH) to detect allelic loss at chromosome 17p and flow cytometry (FC) to test p53 protein overexpression. A total of 17 cases were identified with TP53 deletion and/or protein expression. Both tests correlated in 10 of 17 patients; in six, one or the other abnormality was detected and in one case, with a deletion, flow cytometry failed. Material for direct DNA sequencing was available in 14 of 17 cases. Mutations were found in seven cases. Five of 14 patients with allelic loss and seven of 13 expressing p53 protein had a mutation. These were single-base substitutions and were located in exons 5, 7 or 8. Mutations were not found in 13 of 14 other cases without deletions by FISH or protein expression. The incidence of p53 abnormalities in this series was 15%, with a significant difference between untreated patients (7%) and the pretreated/refractory group (50%; P<0.01). Abnormal p53 was predicted for shorter survival, regardless of the method used. We confirm that p53 abnormalities are more common in refractory CLL and that mutations occur at the known hot spots. Testing for TP53 deletions by FISH and protein expression by FC is an effective and simple way of screening patients who are likely to have aggressive disease. DNA sequencing adds little to these methods in identifying the population at risk.

Isolated bone marrow involvement in diffuse large B cell lymphoma: a report of three cases with review of morphological, immunophenotypic and cytogenetic findings.

Diffuse large B cell lymphoma (DLBL) comprises a heterogenous entity characterized by the presence of large cells, exhibiting a mature B cell phenotype. The high proliferation rate and aggressive disease remain a therapeutic challenge, but the apparent biological diversity permits a risk-stratification model for prognostic grouping through the International Prognostic Index (IPI). Empirical to this approach is the consideration of cytogenetic data, offering an insight into the pathogenetic events which may underlie neoplastic clonal evolution and disease progression. We describe three cases of DLBL presenting with isolated marrow disease, a rare primary finding in this lymphoma. All three cases showed involvement of blood and bone marrow without evidence of splenic or lymph node involvement on imaging studies. Histological and immunophenotypic findings were similar in all three cases, outlining the phenotypic maturity of this disease. Cytogenetic analysis revealed complex karyotypes in the two cases examined. M-FISH (multicolour fluorescent in situ hybridization) performed on bone marrow from case 1 showed several cryptic translocations not evident on G-banding, including a novel translocation between 2p and 9p, and an unbalanced translocation between 14q and 11q. Cytogenetic analysis in case 2 showed abnormalities involving 7q, 9p at the site of the INK4a gene, and the bcl-2 locus, findings confirmed by M-FISH. These cases serve to highlight the biological and cytogenetic heterogenity of DLBL and emphasize the need for complementary investigations in the characterization of this entity.