clonality

A tumor is formed by the clonal expansion of a single precursor cell that has incurred the genetic damage (i.e., tumors are monoclonal).

Types

 B-cell clonality
 T-cell clonality

Clonality assessement

Clonality of tumors can be assessed in women who are heterozygous for polymorphic X-linked markers, such as the enzymes glucose-6-phosphate dehydrogenase (G6PD), iduronate-2-sulfatase and phosphoglycerate kinase.

The most commonly used method to determine tumor clonality involves the analysis of methylation patterns adjacent to the highly polymorphic locus of the human androgen receptor gene (HUMARA).

The frequency of HUMARA polymorphism in the general population is more than 90%, so it is easy to establish clonality by showing that all the cells in a tumor express the same allele.

For tumors with a specific translocation, such as in myeloid leukemias, the presence of the translocation can be used to assess clonality.

Immunoglobulin receptor and T-cell receptor gene rearrangements serve as markers of clonality in B- and T-cell lymphomas, respectively.

References

 Evaluation of T-cell clonality in archival skin biopsy samples of cutaneous T-cell lymphomas using the biomed-2 PCR protocol. Lukowsky A, Muche JM, Möbs M, Assaf C, Humme D, Hummel M, Sterry W, Steinhoff M. Diagn Mol Pathol. 2010 Jun;19(2):70-7. PMID: 20502183