Figure 3.

Double-label immunostains for Sox2 (brown, nuclear) and tumor-specific markers. A) NHL-CNS labeled for CD20 (red, cytoplasmic/membranous) along with nuclear Sox2. The Sox2 immunoreactive nuclei are most numerous in the brain next to the tumor and at the interface with the tumor. No cells are double-positive for CD20 and Sox2. Original magnification 200x. B) Another case of NHL-CNS double-labeled for CD20 and Sox2. The scattered Sox2-immunopositive nuclei are each without associated cytoplasmic/membranous CD20 immunoreactivity. Original magnification 100x. C) High magnification of Sox2-immunopositive nuclei within the NHL-CNS of (B). The absence of CD20-immunopositivity around the Sox2-immunopositive (brown) nuclei is more obvious. Original magnification 400x. D) Another case of NHL-CNS with CD20-negative Sox2-immunopositive cells, and CD20-immunopositive Sox2-negative tumor cells. Original magnification 400x. E) Metastatic carcinoma in brain, double-labeled for Sox2 (brown) and for cytokeratin (CK) (antibody CAM5.2). The tumor cells have CK-immunoreactive cytoplasm with no nuclear Sox2 immunopositivity; the adjacent brain has many cells with Sox2-immunopositive nuclei without cytoplasmic CK, with a few of these entrapped between tumor cells. Original magnification 200x. F) Another metastatic carcinoma in the brain, double-labled for Sox2 (brown) and for cytokeratin (antibody CAM5.2). As in “E”, the tumor cells have CK-positive cytoplasm with no nuclear Sox2 immunoreactivity, while the adjacent brain has cells with Sox2-immunopositive nuclei without any cytoplasmic CK immunoreactivity. Original magnification 200x. G) A metastatic melanoma immunostained for HMB45 (red) and for Sox2 (brown). The Sox2-immunopositive nuclei are mostly within the adjacent brain at the edge of the tumor, and all lack HMB45 cytoplasmic immunoreactivity; the melanoma cells are HMB-45 immunopositive but do not have any Sox2 nuclear immunoreactivity. Original magnification 400x.