CXCR4 and CD26 immunoreactivity and in situ hybridization analysis of SDF-1 expression in an SS skin lesion. (A) Hematoxylin-eosin (H&E) staining of serial sections from a frozen SS skin biopsy reveals the morphologic features of neoplastic T lymphocytes that infiltrate the dermis (magnification × 10/0.30 NA) and (B) (magnification × 40/0.75 NA) where eccrine glands are indicated by white arrows. (C-D) CXCR4-CD3 immunofluorescence shows that the totality of neoplastic CD3-expressing T lymphocytes (green [D]) also express CXCR4 (red [C]) (magnification × 40/0.75 NA). (E) CD26-CD3 costaining analyzed by confocal microscopy shows that the totality of CD3⁺ neoplastic T lymphocytes (red) do not express CD26 on their surface (green) while few CD3-CD26⁺ cells are present. (F) In situ hybridization analysis did not reveal any signal corresponding to specific SDF-1 mRNA expression in neoplastic T lymphocytes. SDF-1 mRNA is detected in epithelial cells of eccrine glands (arrows). Magnification for panels E and F, × 40/1.13 NA.