Immunophenotyping and T-cell receptor γ 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 γ 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 γ 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 γ gene rearrangement studies might help to differentiate the MF cases from the benign cases. (J Am Acad Dermatol 1998;39:554-9.)