Immunohistochemical detection of P-Y-Stat5 and P-S-Akt in neoplastic human mast cells. (A) Adjacent bone marrow (BM) sections from a patient with indolent systemic mastocytosis (ISM) and normal bone marrow (normal BM) sections were stained with an antibody against tryptase for MC detection (brownish staining) and an antibody against P-Y-Stat5 (brownish staining). (B) Similarly, bone marrow sections from a patient with indolent systemic mastocytosis were stained with an antibody against P-Ser⁴⁷³-Akt antibody. Higher magnification of the immunostaining (×400) is also shown.