title: KIT-negative gastrointestinal stromal tumors with a long term follow-up: a new subgroup does exist.
abstract: OBJECTIVE
  To investigate the incidence of KIT immunohistochemical staining in (GI) stromal tumors (GISTs), and to analyze the clinical manifestations of the tumors and prognostic indicators.
  
  
  METHODS
  We retrospectively analyzed 50 cases of previously diagnosed GISTs. Tissue samples were assessed with KIT (CD117 antigen), CD34, SMA, desmin, S-100, NSE, PCNA, Ki-67, and BCL-2 for immunohistochemical study and pathological characteristics were analyzed for prognostic factors.
  
  
  RESULTS
  Fifteen tumors (30%) were negative in KIT staining. A significant association was observed between gender (male patients: 14/15) and KIT-negative staining (P = 0.003).The patients's mean age was 56.6 years. Tumors developed in stomach (n = 8), small intestine (n = 5), large intestine (n = 1) and oesophagus (n = 1). The mean tumor size was 5.72 cm. The mitotic count ranged from 0-29/50 HPF (mean: 3.4) and 73% of tumors showed no necrosis. The majority of the tumors (67%) had dual or epithelioid differentiation. Tumors were classified as very low or low risk (n = 7), intermediate risk (n = 5), and high risk (n = 3) groups. Twelve (80%) patients were alive without evidence of residual tumor for an average period of 40.25 mo (12-82 mo); three patients developed metastatic disease to the liver and eventually died within 2-12 mo (median survival: 8.6 mo).
  
  
  CONCLUSIONS
  A small subgroup of GISTs fulfils the clinical and morphological criteria of these tumors, and lacks KIT expression. These tumors predominantly developed in the stomach, being dual or epithelioid in morphology, which are classified as low risk tumors and presented a better survival status than KIT-positive tumors. The ability to diagnose GISTs still depends on immunohistochemical staining but the research should extend in gene mutations.
authors: Department of Pathology, Athens Medical School, Areteion University Hospital, 1b, Agias Annis Str. 145 63, Kifisia, Greece. k.kontogianni@m2k.gr
authors: Katerina
authors: K
authors: Kontogianni-Katsarou
authors: Constantina
authors: C
authors: Lariou
authors: Eugenia
authors: E
authors: Tsompanaki
authors: Christina
authors: C
authors: Vourlakou
authors: Evi
authors: E
authors: Kairi-Vassilatou
authors: Costas
authors: C
authors: Mastoris
authors: Georgia
authors: G
authors: Pantazi
authors: Agatha
authors: A
authors: Kondi-Pafiti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004938:Esophageal Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005500:Follow-Up Studies; D046152:Gastrointestinal Stromal Tumors / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007414:Intestinal Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D011379:Prognosis; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism; D012189:Retrospective Studies; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism*
chemical_list: D019009:Proto-Oncogene Proteins c-kit