TOX is a specific marker for cutaneous T cell lymphomas

Abstract

Cutaneous T cell lymphoma (CTCL) is characterized by proliferation of clonally expanded T lymphocytes in skin, but without detectable systemic involvement at first diagnosis. The most common subtypes of CTCL are mycosis fungoides (MF) and Sézary syndrome (SS). It is sometimes very difficult to differentiate CTCL from benign inflammatory skin diseases such as atopic dermatitis (AD). Thymocyte selection-associated HMG box factor (TOX) is a DNA-binding factor required for development of CD4 T cells, natural killer T cells, and T regulatory cells. It has been recently reported that TOX serves as a molecular marker for histological diagnosis of early-stage MF. In this study, we evaluated TOX expression in biopsy specimens from various types of cutaneous lymphoma. The followings were enrolled; MF (2 patch, 2 plaque, and 2 tumor samples), SS (2 samples), anaplastic large cell lymphoma (ALCL; 5 samples), adult T cell lymphoma (ATL; 5 samples), diffuse large B dell lymphoma (DLBCL; 5 samples), lymphomatoid papulosis (Lyp; 5 samples), and peripheral T cell lymphoma not otherwise specified (PTL, NOS; 5 samples). We also evaluated TOX expression using skin specimen from healthy controls (5 samples) and AD (2 samples). Dermal atypical lymphocytes showed a high specific nuclear staining in MF/SS, which was consistent with the previous report. Infiltrating lymphocytes in Lyp, and PTL, NOS also showed positive-staining. Interestingly, almost all anaplastic large cells in Lyp were positive for TOX. Tumor cells in ALCL or ATL showed a slightly dim nuclear staining of TOX. In contrast, there was no TOX staining in infiltrating cells of DLBCL, AD, or healthy skin. In summary, TOX may be useful as a specific marker for histological diagnosis of CTCL. JSID AbstractsJournal of Dermatological ScienceVol. 69Issue 2Preview Full-Text PDF