Malignant Smooth Muscle Soft Tissue Tumors. Typical photomicrograph of spindle cell gastrointestinal stromal tumor (A: H&E, ×400) and c-kit stained in the cytoplasm and cytoplasmic membranes (B: Immunohistochemical stain, ×400). Blood vessels within the tumor are negative for c-kit (B).Clinical practice guideline for accurate diagnosis and effective treatment of gastrointestinal stromal tumor in Korea. Kang YK, Kim KM, Sohn T, Choi D, Kang HJ, Ryu MH, Kim WH, Yang HK, Korean GIST Study Gro - Journal of Korean medical science (2010). Not Altered. CC.