Test Details: Fluorescence in situ hybridization (FISH) is a sensitive method to detect smaller genomic changes associated with various haematological malignancies and solid tumours. Deletion of the q arm in Chromosome 13 is observed in mature B-cell lymphoid neoplasms, particularly chronic lymphocytic leukaemia (CLL) and also splenic marginal zone lymphoma and mantle cell lymphoma. The exclusive presence of 13q deletions have been considered as a good prognosis in CLL.