CD7

Recommended positive control: Tonsil, lymph nodes etc

Staining pattern: membrane

CD7 is a pan-T-cell marker, recognizing wide maturation phase of T-cells. NK cells are also positive.

Diagnostic utilities:

Diagnosis of T-cell lymphoma

1) Loss of expression of CD7 indicating high possibility of T-cell lymphoma

Although normal T-cells are positive for CD7, some of peripheral T-cell lymphomas show loss of CD7-expression. This is aberrant phenotype and indicating neoplastic nature. Especially value in diagnosis of mycosis fungoides.

Note: Some inflammatory process may show loss of expression as well.

These photos were gifted by Dr T. Kimura.

Reference:

Am J Dermatopathol. 2002 Feb;24(1):6-16. Low CD7 expression in benign and malignant cutaneous lymphocytic infiltrates: experience with an antibody reactive with paraffin-embedded tissue. Murphy M, Fullen D, Carlson JA.

2) Diagnosis of T-lymphoblastic lymphoma.

This type of T-cell lymphoma is freequently negative for common T-cell markers such as CD3, and CD7 is helpful instead.