Assisting in the classification and follow-up of certain malignant

hematological disorders when bone marrow is not available

Chromosomal abnormalities play a central role in the pathogenesis,

diagnosis, and monitoring of treatment of many hematologic disorders.

Whenever possible, it is best to do chromosome studies for neoplastic

hematologic disorders on bone marrow. Bone marrow studies are more

sensitive and the chances of finding metaphases are about 95%,

compared with only a 60% chance for blood studies. When it is not

possible to collect bone marrow, chromosome studies on blood may

be useful.

When blood cells are cultured in a medium without mitogens, the

observation of any chromosomally abnormal clone may be consistent

with a neoplastic process.

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.

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

An interpretative report will be provided.

The presence of an abnormal clone usually indicates a

malignant neoplastic process.

The absence of an apparent abnormal clone in blood may

result from a lack of circulating abnormal cells and not from an absence

of disease.

On rare occasions, the presence of an abnormality may be

associated with a congenital abnormality and, thus, not related

to a malignant process. When this situation is suspected, follow-up with

a medical genetics consultation is recommended.

We recommend consultation with personnel from the Cytogenetics

Laboratory when considering blood studies for hematologic disorders.

Bone marrow specimens are preferred over peripheral blood specimens

for the diagnosis of neoplastic hematologic disorders. When peripheral

blood must be used, FISH studies may detect some disorders better

than conventional chromosome studies.

FISH studies will detect chromosome anomalies with prognostic

significance much more often than conventional chromosome studies for:

 - Chronic lymphocytic leukemia (CLL).

 - Plasma cell proliferative disorders (PCPDs) such as multiple

   myeloma.

 - FISH studies also may be superior for other hematological

   disorders when compared to conventional chromosome studies

   utilizing blood specimens.

This test is not useful for the following reasons/disorders: multiple

miscarriages, infertility, pregnancy loss, multiple congenital anomalies,

developmental delay, Down syndrome, Turner syndrome, premature

ovarian failure, amenorrhea, ambiguous genitalia, and other congenital

abnormalities. The appropriate test for these situations is #8696

"Chromosome Analysis, for Congenital Disorders, Blood."

Interfering factors

   Technical:

      - Cell lysis caused by forcing blood quickly through the needle

        at collection

      - Use of an improper anticoagulant (sodium heparin is best) or

        improperly mixing the blood with the anticoagulant

      - Excessive transport time

      - Exposure of the specimen to temperature

   Biological:

      - Abnormalities missed due to sampling error

      - Subtle structural chromosome abnormalities may be missed

        occasionally

      - Neoplastic cells not dividing or not circulating in the bloodstream

Dewald GW, Ketterling RP, Wyatt WA, Stupca PJ:  Cytogenetic

studies in neoplastic hematologic disorders. In Clinical

Laboratory Medicine, 2nd edition. Edited by KD McClatchey.

Baltimore, Williams & Wilkens, 2002, pp 658-685