CD7

Summary

CD7 is a pan T-cell marker that is useful for identifying T cells at very early stages of maturation. However, its value is limited by a high frequency of aberrant expression by other lineages that means caution is required in its interpretation

In some mature T cell disorders variation of expression of CD7 can have diagnostic value

Background

CD7 is a transmembrane protein that supports T cell interactions with B cells during lymphoid development. Expression is acquired during thymic development of T cells appearing before other T-lineage markers, and expression is retained by mature T cells.

Diagnostic Use

• CD7 Has consistent expression by T-all from an early (pro-T) stage of maturation; however, expression is recognised in AML and some B-ALL
• loss of CD7 expression occurs in mycosis fungoides and Sézary and therefore can contribute to diagnosis of these disoders
• Strong expression of CD7 is seen in T-PLL, while lower in ATLL and LGL have weak expression

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