Immunohistochemical features of pituicytomas. All tumors showed strong and diffuse nuclear positivity for TTF-1 (a). A subset of tumors were positive for S100, GFAP (focal staining showed), EMA, synaptophysin and SSTR2A (b, c, d, e and f, respectively). The proliferation index by Ki-67 was low for non-atypical pituicytomas (g). One tumor (patient #1) was positive for BRAF V600E (h). The majority of tumors were strongly positive for pERK (i) though one was negative (j). a and f at 100x; b, c, d, e, g, h, i and j at 200x.