Double immunohistochemical technique useful for differential diagnosis of mycosis fungoides

Abstract

The TNM Classification of Malignant Tumors (TNM) comprises Stages 1–4 depending on the range and characteristics of skin lesions and the presence or absence of abnormal peripheral lymph nodes or internal organ lesions. Since therapeutic strategies and survival rate differ greatly depending on the stage, early detection and medical treatment are important. We examined the usefulness of the double immunohistochemical technique for the differential diagnosis of mycosis fungoides. The main reason why mycosis fungoides was targeted in this study was that it is positive for CD3 and CD4 T-cell markers, thus leading to the elimination or reduction of CD7. First, CD3 and CD7 were double-stained. After that, the secondary antibodies simultaneously reacted to their corresponding primary antibodies as well. Then two coloring substances with different tones were used to stain CD3 blue and CD7 brown. We let the strong color mask the weak color by having the colors resulting from the simultaneous positive reactions overlap with one another. As a result, only cells with mycosis fungoides appeared blue because of CD3 positive and CD7 negative reactions. Normal cells and cells with inflammation appeared brown because the CD3 positive reaction (blue) was masked by the CD7 positive reaction (brown). This staining method is extremely simple requiring only a short staining time.