title: A study of histopathological assessment criteria for assessing malignancy of gastrointestinal stromal tumor, from a clinical standpoint.
abstract: BACKGROUND
  As no established histopathological criteria exist for assessing the malignant potential of gastrointestinal stromal tumor (GIST), recurrence or metastasis is occasionally observed in lesions diagnosed histopathologically as benign. The present study aimed to clarify the histopathological criteria for assessing the malignancy of GIST, from a clinical standpoint.
  
  
  METHODS
  The subjects were 22 patients with GIST expressing CD117 (c-kit) and/or CD34, who were followed up for more than 2 years. Clinically, GIST malignancy was diagnosed if any of the following criteria were met: peripheral invasive growth, lymph node metastasis, metastasis to another organ, peritoneal dissemination, recurrence, or death. GIST was also categorized as either benign or malignant by a new histological malignancy classification system, based on the determination of significant factors indicating malignancy in the clinical classification system above.
  
  
  RESULTS
  Significant factors for malignancy identified in the clinical malignancy classification were: tumor hemorrhage/necrosis (present vs absent; P = 0.0053), tumor size (<5 cm vs > or =5 cm; P = 0.0022), and Ki-67 labeling index (<3% vs > or =3%; P = 0.0002). A new histological malignancy classification, based on a combination of these three factors, was developed. A significant correlation existed between the clinical system and the new histological malignancy classification system (P = 0.0008). The recurrence-free survival rate was 100% in the histologically benign cases and 37.5% in the histologically malignant cases (P = 0.0012).
  
  
  CONCLUSIONS
  The new histological malignancy classification for GIST was demonstrated to be useful from a clinical standpoint.
authors.affiliation: Department of Surgery, Nippon Medical School Chiba Hokusoh Hospital, 1715 Kamagari, Inbamura, Inbagun, Chiba, 270-1694, Japan.
authors.forename: Kimiyoshi
authors.initials: K
authors.lastname: Yokoi
authors.forename: Noritake
authors.initials: N
authors.lastname: Tanaka
authors.forename: Kyono
authors.initials: K
authors.lastname: Shoji
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ishikawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Seya
authors.forename: Koji
authors.initials: K
authors.lastname: Horiba
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kanazawa
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Yamashita
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ohaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Tajiri
mesh_terms: D000328:Adult; D000368:Aged; D018952:Antigens, CD34 / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001707:Biopsy, Needle; D016022:Case-Control Studies; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D046152:Gastrointestinal Stromal Tumors / Q000401:mortality / Q000473:pathology* / Q000628:therapy; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology*; D009367:Neoplasm Staging; D011336:Probability; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D015996:Survival Rate
chemical_list: D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D019009:Proto-Oncogene Proteins c-kit