T-cell has been applied clinically as a technique to demonstrate clonality of T lymphocytes.1-3 Although often difficult to demonstrate, clonality is considered to be a sine qua non of malignancy. The occurrence of a unique chromosomal translocation (eg, the translocation of the long arm of chromosome 22, the Philadelphia1 chromosome) in chronic myelogenous leukemia is strong evidence for the clonal derivation of this malignancy. It is understood that the malignant transformation of the leukemic cells must occur at the time of, or after, the Philadelphia1 translocation so that each malignant cell contains the translocated chromosome. The immunohistochemical demonstration that almost every cell in a proliferation of B lymphocytes expresses one immunoglobulin light chain (either κ or X) is evidence that the cells are likely to all be members of a single clone that may be malignant. Again, the malignant transformation of the B lymphocyte must occur at
Bleicher PA, Balk SP. T-Cell Receptor Gene Rearrangements: Progress and Promise. Arch Dermatol. 1988;124(3):359–363. doi:10.1001/archderm.1988.01670030025016
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