Basal cell carcinoma arising from xeroderma pigmentosum: a case report and an immunohistochemical study.

We describe a 26-year-old Japanese patient with basal cell carcinoma arising from xeroderma pigmentosum (XP). Immunohistochemical staining revealed dense infiltration of CD163(+) M2 macrophages, together with Foxp3(+) regulatory T cells. Interestingly, MMP9, which was reported as one of the functional markers for immunosuppressive macrophages, was also detected in the CD163(+) M2 macrophage-infiltrated areas. Our case suggests the immunological background of tumor development in a patient with XP.