Immunophenotyping and T-cell receptor gamma gene rearrangement analysis as an adjunct to the histopathologic diagnosis of mycosis fungoides.

Background: The histopathologic diagnosis of mycosis fungoides (MF) may be difficult.
Objective: Our purpose was to evaluate the role of immunophenotyping and T-cell receptor (TCR) gene rearrangement studies as an adjunct to the histopathologic diagnosis of MF.
Methods: Immunohistochemical studies with antibodies to CD4, CD5, CD7, and CD8 and TCR gamma gene rearrangement analysis with a polymerase chain reaction were performed on fresh-frozen material of patients with "classic" histology of MF, "inconclusive" histology, and benign inflammatory dermatoses.
Results: Clonal TCR gamma gene rearrangements were found in 11 of 16 (69%) of classic MF cases, in 3 of 19 (16%) of inconclusive cases, and in none of the 12 inflammatory dermatoses cases (P < .05 and P < .001, respectively). Only the mean CD7 counts were statistically significantly different between these 3 groups (MF < inconclusive < inflammatory).
Conclusion: Inconclusive histology is probably a heterogeneous group in which CD7 counts and TCR gamma gene rearrangement studies might help to differentiate the MF cases from the benign cases.