Figure 3
From: Mutually exclusive recurrent KRAS and MAP2K1 mutations in Rosai–Dorfman disease
MAP2K1-mutated Rosai–Dorfman disease, nasopharynx (case 12). (a) Medium-power image of nasopharynx with sheets of histiocytes admixed with lymphocytes and plasma cells (× 200). (b) Higher magnification shows numerous histiocytes engulfing lymphocytes, plasma cells, and neutrophils (× 400). (c) Immunostain for S-100 is positive in histiocytes and negative in engulfed lymphocytes (× 400). (d) Immunostain for p-ERK is positive in the nucleus and cytoplasm of a subset of Rosai–Dorman histiocytes (× 500).
