Cytogenetics - oncology

Specimen:

Consult pathologist prior to specimen collection.

All specimens must be transported to the laboratory immediately after collection.

Bone marrow aspirate: 1-2 mL in sterile, preservative-free heparin (and a sample in EDTA if molecular testing is required eg, PCR-based testing).

Peripheral blood (if sufficient abnormal cells are present): 10 mL in sterile, preservative-free heparin (and a sample in EDTA if molecular testing is required e.g. PCR-based testing).

Lymph node or tumour biopsy: at least 1.5 cm diameter biopsy in sterile container, with sufficient tissue culture medium to cover the specimen.

Effusions (eg, ascites, pleural fluid): 5-30 mL in sterile container.

Method:

Direct preparation and/or short term cultures are generally used. Chronic lymphoproliferative disorders may require mitogen stimulation and 72 h culture. Solid tumour specimens may require even longer culture times depending on the tumour type.

Results may take from 2 days to 3 weeks for completion. The type and duration of culture and the culture medium used may vary for the indication and specimen type.

Cytogenetic harvesting, slidemaking, banding and karyotyping are performed on all specimens. FISH may be used to identify specific chromosomal abnormalities. See also Fluorescence in situ hybridisation.

Molecular testing based on PCR (polymerase chain reaction) is available for detection of specific chromosomal abnormalities, such as the BCR-ABL fusion gene typically seen in Chronic myeloid leukemia.

Microarray methods are used in some laboratories for oncology testing, but this is not currently widespread.

Note that for molecular testing (PCR or microarray), a sample collected in EDTA is generally required.

Application:

Haematological and solid malignancies, including Wilms' tumour, Neuroblastoma, Rhabdomyosarcoma, Synovial sarcoma, and Ewing's sarcoma.

Diagnosis, assessment of prognosis, disease staging, monitoring response to therapy and detection of residual disease.

Interpretation:

Findings are reported in terms of numerical and/or structural chromosome abnormalities (eg, deletions, translocations) - consult pathologist.

Non-random chromosome abnormalities occur in Acute lymphoblastic leukaemia; Acute myeloid leukaemia; Chronic myeloid leukaemia and other Myeloproliferative neoplasms; Myelodysplastic syndromes; Lymphoma (non-Hodgkin); Plasma cell myeloma and some solid tumours.

Reference:

Rooney DE ed. Human Cytogenetics, Malignancy and Acquired Abnormalities, a Practical Approach. 3rd ed. Oxford University Press 2001.