Small gastrointestinal stromal tumor in the stomach: identification of precursor for clinical gastrointestinal stromal tumor using c-kit and α -smooth muscle actin expression

• Published in: Human pathology 2013-12, Vol.44 (12), p.2628-2635
• Main Authors: Mikami, Tetuo, MD, Nemoto, Yuta, MD, Numata, Yoshiko, BSc, Hana, Kiyomi, Nakada, Norihiro, MD, Ichinoe, Masaaki, MD, Murakumo, Yoshiki, MD, Okayasu, Isao, MD
• Format: Article
• Language: English
• Subjects: Actins - genetics; Actins - metabolism; Aged; Aged, 80 and over; Cell Transformation, Neoplastic - genetics; Cell Transformation, Neoplastic - pathology; Female; Gastrointestinal stromal tumor; Gastrointestinal Stromal Tumors - diagnosis; Gastrointestinal Stromal Tumors - genetics; Gastrointestinal Stromal Tumors - metabolism; Humans; KIT mutation; Male; Middle Aged; Muscle, Smooth - metabolism; Muscle, Smooth - pathology; Mutation; Pathology; Proto-Oncogene Proteins c-kit - genetics; Proto-Oncogene Proteins c-kit - metabolism; Small GIST; Stomach; Stomach - metabolism; Stomach - pathology; Stomach Neoplasms - diagnosis; Stomach Neoplasms - genetics; Stomach Neoplasms - metabolism; Tumorigenesis
• ISSN: 0046-8177; 1532-8392
• DOI: 10.1016/j.humpath.2013.07.020

Summary Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the digestive tract. To find precursors for clinical GISTs of the stomach, small gastric stromal tumors of less than 3 cm were collected and examined immunohistochemically with analysis of the KIT mutation. Sixty-eight of 74 lesions were classified into 4 representative groups according to the expression of c-kit and α -smooth muscle actin ( α SMA): group A, c-kit diffusely positive and α SMA negative (18 cases); group B, c-kit diffusely positive and α SMA focally positive (13); group C, c-kit focally positive and α SMA diffusely positive (27); and group D, c-kit negative and α SMA diffusely positive (10). Of the 4 groups, groups A and B of c-kit diffuse expression showed higher cellularity and labeling indices of p27Kip1 and Ki-67 than did groups C and D of diffuse α SMA expression. Incidence of KIT exon 11 mutation in groups A and B was 86% (25/29), whereas that in groups C and D was 0% (0/20). Small gastric stromal tumors with c-kit diffuse expression were considered precursors for clinical GIST because they were significantly different from c-kit focally positive or negative tumors. The mutation of KIT is considered as an early event in tumorigenesis of GIST.