Increase of DC-LAMP+ mature dendritic cell subsets in dermatopathic lymphadenitis of mycosis fungoides

Background: Little is known about the immunological milieu of the skin-draining lymph nodes (LNs) in mycosis fungoides (MF). Objectives: We studied dendritic cell (DC) subsets in the dermatopathic lymphadenitis of MF patients. Methods: We immunohistochemically examined DC subsets and their distribution in 16 LN samples from 14 patients with MF (N1 LN, eight patients; N2, four; and N3, four), and we compared them with non-metastatic sentinel LNs from eight patients with melanoma. Results: The number of S-100 protein+ DCs was markedly increased in the LNs from the MF patients and the major component was DC-LAMP+ mature DCs in the outer and paracortex areas, where DC-SIGN+ immature DCs were relatively decreased in proportion. In contrast, DC-SIGN+ cells were relatively increased in proportion compared to DC-LAMP+ cells in the medulla. Although no significant difference was observed in the proportions of CD1a+ or Langerin+ DCs among the N1, N2, and N3 nodes, CD163+ M2-type macrophages were increased in number in the N2 and N3 nodes. Conclusions: Our observations indicate that mature DCs accumulate in the outer and paracortex areas in dermatopathic lymphadenitis and M2-type macrophages might increase in number during disease progression.