Contribution of T-cell receptor gamma gene rearrangement by polymerase chain reaction and immunohistochemistry to the histological diagnosis of early mycosis fungoides

OBJECTIVE: To study the role of immuno-histochemistry and T-cell receptor (TCR) gamma gene rearrangement analysis in the diagnosis of mycosis fungoides (MF).

METHODS: The study design was retrospective, and 73 cases were selected from the archive of the Pathology Department, School of Medicine, Cukurova University, Adana, Turkey, between January 2004 and December 2009. Thirty-nine MF cases with classical histomorphology, 16 cases with suspicious histomorphology for MF as the inconclusive group, and 18 cases with benign inflammatory dermatoses as the control group were involved in the study. The slides were evaluated for the presence or absence of the histopathological criteria for MF. Immunohistochemically, CD3, CD4, and CD8 were performed in all cases, and their counts and CD4/CD8 ratio were noted. Presence clonal TCR gamma gene rearrangement was evaluated by polymerase chain reaction (PCR).

RESULTS: The histopathological parameters suggestive of MF were epidermotropism (p=0.000), presence of Pautrier microabscess (p=0.004), and atypical lymphocyte (p=0.000). Immunohistochemically, CD4 percentage (p=0.006) and CD4/CD8 ratio (p=0.010) were statistically significant parameters with univariate analysis. Clonality was present in 76.9% of MF cases and 37.5% in the inconclusive group. Four of 6 clonality positive cases in the inconclusive group were diagnosed as MF in rebiopsies. The CD8 percentage was not statistically different between the 3 groups.

CONCLUSION: In suspicious cases, CD4/CD8 ratio and TCR gamma gene rearrangement can support histopathology in early MF.