Cytogenetic analysis plays an important role in the diagnosis, prognosis, management and treatment of haematological malignancies. Karyotyping and FISH now play an important role in the diagnostic profile of haematologic disorders such as Leukemia and Lymphoma. Good-prognosis patients have been spared unnecessary treatment, while more intensive treatment in some poor prognosis cases has improved the outcome of these patients.
Karyotyping in haematological malignancies
Several specific rearrangements occur in the chromosomes in different types of leukemia like CML, CLL, AML, ALL, MPD and MDS. The treatment varies in certain abnormalities. Hence karyotyping is essential to find out the type of abnormality present in individual cases. A bone marrow sample (which has actively dividing cells) is aspirated from the patient and cultured under various conditions to obtain chromosomes. These are G-banded and analyzed for aneuploidy, translocations, deletions and other abnormalities. Multiple cultures are set up, as the abnormality may not be detected in all cultures. Acquired chromosome abnormalities are occasionally seen in only a few poor quality cells, hence detailed analysis is carried out. However, subtle translocations can never be ruled out by karyotyping and FISH is preferable if the probes are available.
Sample : The latest WBC count should be sent along with the sample. The quantity of bone-marrow required is inversely proportional to the WBC count. For example, 1.5 – 2ml bone-marrow in a sodium heparin vaccutainer is required for a normal WBC count. If the WBC count is low, proportionately more bone-marrow should be sent, if possible. The sample should be transported at room temperature.
FISH for haematological malignancies
The FISH technique is very useful in diagnosis, prognosis, and management of leukemia patients and in the detection of minimal residual disease.
In order to periodically monitor the progress of therapy in BCR/ABL fusion (Philadelphia +ve) and PML/RARA fusion (AML-M3) cases, semi-quantitative FISH can be carried out on heparinized blood instead of bone-marrow. In case a relapse is suspected, karyotyping from bone-marrow is again repeated to look for clonal evolution.
The double-fusion BCR/ABL and PML/RARA probes reduce the chances of false positivity. FISH is also useful in complex translocations leading to a masked Philadelphia chromosome, which may be missed on karyotyping.
List of our FISH Probes in Leukemia
- BCR/ABL dual colour dual fusion probe for t(9;22)
- PML/RARA dual colour dual fusion probe for t(15;17)
- AML/ETO dual colour dual fusion probe for t(8;21)
- 8q24 breakapart probe for Burkits Lymphoma
- Inversion 16 breakapart probe
- RARA (17q12-q21) breakapart probe
- del(13q14)
- Deletion 13q14.3 and 13q34 in Myltiple Myeloma
- CLL panel to check for deletions of 11q23, p53, 13q14.3, 13q34 and Trisomy 12
Sex mis-matched Bone Marrow Transplant
In cases like CML, aplastic anemia, where sex-mismatched bone-marrow transplantation is carried out, determination of the percentage of XX and XY cells by FISH gives an indication of the success of a transplant.
Sample: 2-3 ml Bone marrow in heparin vaccutainer (Green top) with latest WBC count transported at room temperature.
Bladder cancer
We have introduced a new FISH-based test at Jaslok Hospital using the Vysis UroVysion Kit. This is the first FDA-cleared genomic DNA-probe test for monitoring recurrence of bladder cancer. The test is designed to detect aneuploidy for chromosomes 3, 7, 17, and loss of the 9p21 locus (containing the p16 tumor suppressor gene), which is one of the most common alterations in urothelial carcinoma. Results from the UroVysion Kit are intended for use in conjunction with current standard diagnostic procedures, as an aid for initial diagnosis of bladder carcinoma in patients with hematuria, and subsequent monitoring for tumor recurrence in patients previously diagnosed with bladder cancer.
- UroVysion detects chromosomal abnormalities associated with the development and progression of bladder cancer.
- UroVysion in conjunction with cystoscopy delivers the best balance of sensitivity (97%) and specificity (95%).
- It allows for more accurate patient monitoring, by detecting bladder cancer recurrence up to 6 months sooner than current diagnostic methods.
- It is more sensitive than cytology and reduces the false negatives.
- The UroVysion kit detects all stages and grades of bladder cancer. It is highly sensitive for more dangerous higher grade and stage tumors.
- The test is not affected by BCG immunotherapy.
Early detection of high grade disease is critical to increased survival.
