Dermal infiltrates of cutaneous T-cell lymphomas with epidermotropism but not other cutaneous lymphomas are abundant with langerin⁺ dendritic cells.

BACKGROUND: The Langerhans cell (LC) hypothesis suggests that cutaneous T-cell lymphomas (CTCL) are diseases of chronic T-cell stimulation by LC-mediated antigen presentation. OBJECTIVE: To investigate a broad panel of CTCL and cutaneous B-cell lymphomas (CBCL) for the spatial association of langerin(+) dendritic cells (DC) with T and B cells in the skin, respectively. METHODS: Fifty-five specimens of CTCL and 10 of CBCL were double-stained with monoclonal antibodies against langerin and CD3 or CD20, respectively, and evaluated by confocal laser scan microscopy. RESULTS: Dermal infiltrates in mycosis fungoides (n = 38), primary cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoma (n = 3) and primary cutaneous peripheral T-cell lymphoma, unspecified (n = 3) were characterized by a high frequency of dermal langerin(+) DCs. These cells were exclusively present in the malignant infiltrates. No direct co-localization of CD3 and langerin could be resolved. Dermal langerin(+) cells were detected only in one of six primary cutaneous anaplastic large cell lymphomas (C-ALCL), characterized by epidermotropism. In other C-ALCL cases (five of six), in lymphomatoid papulosis (n = 3), subcutaneous panniculitis-like T-cell lymphoma (n = 2), and all variants of CBCL no dermal langerin(+) DCs could be found. CONCLUSIONS: Langerin(+) DCs are abundant in the dermal infiltrates of T-cell lymphomas with specific involvement of the epidermis. This might indicate that immature LC and neoplastic T cells interact and gives rise to further studies to characterize the phenotype of the langerin(+) cell population described here and its role in the pathology of CTCL.