Fig. 4
From: Identification of diverse activating mutations of the RAS-MAPK pathway in histiocytic sarcoma
Immunohistochemical validation of candidate driver genes. a A case of histiocytic sarcoma (i-H&E x400 magnification, ii-H&E x1000 magnification; arrowheads show mitotic figures; iii-iv-immunohistochemistry x400 magnification) harboring a NF1 loss-of-function mutation and two-copy deletion involving 9p21.3 including CDKN2A (lower). The tumor showed diffuse and strong expression of p-ERK (v-x400 magnification). Immunohistochemistry for p16 demonstrated loss of staining in tumor cells (arrowheads show intact expression of p16 in background inflammatory cells; vi-x1000 magnification). b A case of histiocytic sarcoma (H&E x400 magnification) presenting as a rectal mass with PTEN mutation involving the N-terminal cytoplasmic localization sequence. Immunohistochemistry for p-S6 protein showed diffuse and strong expression (x400 magnification). Immunohistochemistry for PTEN (x1000 magnification) showed loss of cytoplasmic protein expression in tumor cells and abnormal nucleolar localization (arrowheads). Note intact expression of PTEN in background stromal and inflammatory cells (arrow)
