Abstract: CD20 is a B-cell specific antibody and the most important antibody in the differential diagnosis of T-cell lymphomas. In recent years, many cases of T-cell lymphomas with positive for CD20 have been reported. The large cell transformation of MF can occur in the whole course of the disease, but it is usually common in the tumor stage. The large cell transformation is often a sign of poor prognosis. We report a case of mycosis fungoides with large cell transformation positive for CD20.

Key words: mycosis fungoides, large cell transformation, CD20, T-cell lymphoma