For assessment of TP53 loss (del17p) by FISH, please refer to the South East Scotland Cytogenetics Service.

CLL samples contain a mixture of leukaemia and non-leukaemia cells.  Since TP53 mutations are acquired within leukaemia cells, they will not be present within non-CLL cells within the sample. Therefore, it is important to be aware of the approximate percentage of leukaemia cells within the sample. The assay carries a limit of detection of 15% and therefore a low level TP53 mutation may not be detected by this approach.

For samples with a likely low level leukaemia percentage, Lymphoprep isolation of mononuclear cells will be performed. Hence, please inform the laboratory, where possible, of the total lymphocyte count and total white cell count in the sample

​TP53 mutation assessment is performed using Sanger sequencing to assess and identify sequence variants in exons 2a, 2d, 3, 4b, 5, 6, 7, 8, 10 and 11 of the TP53 gene (LRG_321 specific exon numbering). In most cases, a TP53 mutation is associated with loss of chromosome 17p [del17p]. However, some patients may carry a TP53 mutation without accompanying loss of chromosome 17p. Mutations in the TP53 gene are associated with chemotherapy resistance and poor prognosis in patients with CLL.

Assessment of the IGHV mutation status can also be performed.

For clinical advice on appropriate investigations and advice for the interpretation of test results, please contact us​.