Interpretive Handbook

Chromosomal abnormalities play a central role in the pathogenesis, diagnosis, and monitoring of treatment of many hematologic disorders. Cytogenetic studies on bone marrow may be helpful in many malignant hematologic disorders as the observation of a chromosomally abnormal clone may be consistent with a neoplastic process.

Certain chromosome abnormalities may help classify a malignancy. As examples, the Philadelphia (Ph) chromosome, also referred to as t(9;22)(q34;q11.2), is usually indicative of chronic myelogenous leukemia (CML) or acute leukemia; t(8;21)(q22;q22) defines a subset of patients with acute myelogenous leukemia, M2; and t(8;14)(q24.1;q32) is associated with Burkitt leukemia/lymphoma.

Cytogenetic studies are also used to monitor patients with hematologic disorders and may identify disease progression, such as the onset of blast crisis in CML, which is often characterized by trisomy 8, isochromosome 17q, and multiple Ph chromosomes.

See An Expanded Algorithm for the Laboratory Evaluation of Suspected Multiple Myeloma in Special Instructions. Also see Diagnosis and Monitoring of Multiple Myeloma in Publications.

Assisting in the diagnosis and classification of certain malignant hematological disorders

Evaluation of prognosis in patients with certain malignant hematologic disorders

Monitoring effects of treatment  

Monitoring patients in remission

To insure the best interpretation, it is important to provide some clinical information to verify the appropriate type of cytogenetic study is performed.

The following factors are important when interpreting the results:

-Although the presence of an abnormal clone usually indicates a malignant neoplastic process, in rare situations, the clone may reflect a benign condition.

-The absence of an abnormal clone may be the result of specimen collection from a site that is not involved in the neoplasm or may indicate that the disorder is caused by submicroscopic abnormalities that cannot be identified by chromosome analysis.

-On rare occasions, the presence of an abnormality may be associated with a congenital abnormality that is not related to a malignant neoplastic process. Follow-up with a medical genetics consultation is recommended.

-On occasion, bone marrow chromosome studies are unsuccessful. If clinical information has been provided, we may have a FISH study option that could be performed.

In some cases, FISH studies may detect some disorders better than conventional chromosome studies:

-For chronic lymphocytic leukemia (CLL), FISH studies will detect chromosome anomalies with prognostic significance much more often than conventional chromosome studies. We suggest FCLL/83089 Chronic Lymphocytic Leukemia (CLL), FISH.

-For plasma cell proliferative disorders (PCPDs) such as multiple myeloma, FISH studies will detect chromosome anomalies with prognostic significance much more often than conventional chromosome studies. We suggest FPCPD/83358 Plasma Cell Proliferative Disorder (PCPD), FISH.

Interfering factors

Technical:

-Excessive transport time

-Too little bone marrow specimen

-Not processing the bone marrow as indicated before shipping the specimen

-Not sending the first aspirate from the patient's bone marrow draw

Biological:

-Abnormalities missed due to sampling error

-Subtle structural chromosome abnormalities may be missed occasionally

-Neoplastic cells not dividing

46,XX or 46,XY. No apparent chromosome abnormality.

An interpretative report will be provided.

Dewald GW, Ketterling RP, Wyatt WA, Stupca PJ: Cytogenetic studies in neoplastic hematologic disorders. In Clinical Laboratory Medicine. Second edition. Edited by KD McClatchey. Baltimore, Williams and Wilkens, 2002, pp 658-685