Value of TOX Immunoexpression in the Diagnosis of Early Mycosis Fungoides

The lack of a specific marker to differentiate malignant from reactiveT-cells makes a definite diagnosis difficult in patients suspected of having mycosisfungoides. This study has evaluated value of thymocyte selection-associated highmobility group box factor expression in the differentiation of early mycosis fungoidesfrom a benign inflammatory dermatosis.We selected 22 mycosis fungoides cases, 18 cases suspicious for mycosisfungoides, and 12 cases of eczematous dermatitis from patients who attendedDermatology Clinic, Shiraz University of Medical Sciences (2008-2015). The obtainedskin biopsies were immunostained for thymocyte selection-associated high mobilitygroup box factor antigen in addition to pan T cell markers. The slides were evaluatedfor the percentage of tumor cells and intensity of immunoreactivity. From 22 cases of mycosis fungoides, 40.9% showed massive infiltrationof thymocyte selection-associated high mobility group box factor-positive lymphocytes(>30%) with high (3+) intensity in the epidermis; there was no case negative forthymocyte selection-associated high mobility group box factor expression. Only oneeczematous dermatitis case had expression of thymocyte selection-associated highmobility group box factor-positive lymphocytes (>30%) with high intensity and 4 caseswere negative for thymocyte selection-associated high mobility group box factorexpression. The frequency of thymocyte selection-associated high mobility groupbox factor expressing lymphocytes was higher in biopsies from mycosis fungoidescompared to eczematous dermatitis (P<0.05). CD7- cases expressed more thymocyteselection-associated high mobility group box factor-positive lymphocytes in the dermisand epidermis, which were significantly correlated (P=0.013). Thymocyte selection-associated high mobility group box factor, as apositive marker, in combination with pan T cell markers (especially CD7-) can be usefulto detect mycosis fungoides malignant lymphoid cells.