title: The clinicopathologic observation, c-KIT gene mutation and clonal status of gastrointestinal stromal tumor in the sacrum.
abstract: BACKGROUND
  It is very rare that gastrointestinal stromal tumor (GIST) occurs in the sacrum. Only one case of GIST occuring in the sacral region, with intracranial metastasis, has been reported in the literature. Moreover, only few cases have been published in literature about its clonal origin.
  
  
  METHODS
  In this report, we present a rare case of GIST occuring in the sacrum and describe its clinicopathologic features, c-KIT gene mutation and clonal status. Microscopically, the lesion was composed of spindle cells arranged in cords, knitted and whirlpool patterns. Trabecula of bone were found in the lesion. The cytoplasm of tumor cells were abundant, and the nuclei were fusiform. Mitotic figures were rare. Immunohistochemically, the tumor cells showed positive reactivity for CD117 and CD34. On mutation analysis, a c-KIT gene mutation was found in exon 11. The result of clonal analysis demonstrated that the GIST was monoclonal.
  
  
  CONCLUSIONS
  In summary, we showed that tumor material, phenotypically identical with GISTs was found in the sacrum. It is difficult to differentiate GISTs from other spindle cell tumors, hence the need for immunohistochemistry, the examination of c-KIT gene amplification and sequencing.
authors.affiliation: Department of Pathology, Tangdu Hospital, the Fourth Military Medical University, Xi'an 710038, Shaanxi Province, PR China. gongli1976@126.com
authors.forename: Li
authors.initials: L
authors.lastname: Gong
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Li
authors.forename: Hua-Dong
authors.initials: HD
authors.lastname: Zhao
authors.forename: Jian-Ye
authors.initials: JY
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism; D001483:Base Sequence; D001859:Bone Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology*; D005091:Exons / Q000235:genetics; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D012447:Sacrum / Q000378:metabolism / Q000473:pathology*
chemical_list: D018952:Antigens, CD34; D019009:Proto-Oncogene Proteins c-kit