CD7

Although it has been recently stated that antibodies are effective on fresh-frozen tissue only2, others find successful staining of paraffin-embedded tissues.

Immunohistochemical expression

• T-cells including prothymocytes and thymocytes. It is positive in all CD8+ and most CD4+ T-cells.

• Positive in most T-ALL/T-LBL

• Most NK cells

• Some acute myelogenous leukaemias

Diagnostic utility

• Diagnosis of T-cell lymphomas. Aberrant loss of expression may occur in T-cell lymphomas and may help to distinguish them from reactive T-cell proliferations, in which role it is more sensitive than CD2 and CD51. Loss of CD7 is usual in mycosis fungoides/Sezary syndrome. However, similar antigen loss has been reported in inflammatory dermatoses1, including lymphomatoid papulosis and PLEVA.

References

1Liu V., McKee PH. Cutaneous T-cell lymphoproliferative disorders; approach for the surgical pathologist: recent advances and clarification of confused issues. Advances in Anatomic Pathology 2002;9:79-100.

2Leong A S-Y, Cooper K and Leong FJ W-M. Manual of diagnostic antibodies for immunohistology. 2nd edition, 2003

©SMUHT/PW Bishop