CADM1 is a diagnostic marker in early-stage mycosis fungoides: Multicenter study of 58 cases.

Abstract

Mycosis fungoides (MF) is the most common cutaneous T-cell lymphoma. Early-stage MF patches or plaques often resemble inflammatory skin disorders (ISDs), including psoriasis and atopic dermatitis. Cell adhesion molecule 1 gene (CADM1), which was initially identified as a tumor suppressor gene in human non-small cell lung cancer, has been reported as a diagnostic marker for adult T-cell leukemia/lymphoma. We investigated CADM1 expression in MF neoplastic cells, especially during early stages, and evaluated its usefulness as a diagnostic marker for MF. We conducted a retrospective study by using immunohistochemical staining and confirmed the expression of CADM1 in MF. In addition, we compared CADM1 messenger RNA expression in microdissected MF samples and ISD samples. In the overall study period, 55 of 58 MF samples (94.8 %) stained positive for CADM1. None of the 50 ISD samples showed positive reactivity (P < .0001). We found CADM1 messenger RNA expression in the intradermal lymphocytes of patients with MF but not in those of patients with an ISD. We did not conduct a validation study for MF cases in other institutions. CADM1-positive cells can be identified in early stages with fewer infiltrating cells and may be useful as a diagnostic marker for early-stage MF.