title: Expression of glypican 3 in placental site trophoblastic tumor.
abstract: BACKGROUND
  Glypican-3 (GPC3) is a membrane-bound heparan sulfate proteoglycan that functions in embryonic cell growth and differentiation and is highly expressed in the placenta. GPC3 is mutated in Simpson-Golabi-Behmel syndrome, which is characterized by tissue overgrowth and an increased risk of embryonal malignancies. GPC3 has also been implicated in sporadic cancer, particularly hepatocellular carcinoma, for which it has been shown to be a useful diagnostic marker. Although GPC3 expression has been studied in non-neoplastic placental tissue, its presence in gestational trophoblastic diseases has not been previously explored. The purpose of this study was to investigate the immunohistochemical expression of GPC3 in placental site trophoblastic tumor (PSTT), a very rare gestational trophoblastic neoplasm which may be morphologically confused with non-trophoblastic tumors, and to assess its possible utility as a diagnostic marker.
  
  
  METHODS
  Fifteen cases of PSTT, as well as samples from placental site nodule (PSN) (n = 2), leiomyosarcoma (n = 1), leiomyoma (n = 1), invasive cervical squamous cell carcinoma (n = 7) and endometrial adenocarcinoma (n = 11) were examined. Immunoreactivity was semi-quantitatively evaluated as negative (0, < 5% of cells stained), focally positive (1+, 5-10% of cells stained), positive (2+, 11-50% of cells stained) or diffusely positive (3+, > 50% of cells stained). Staining intensity for each subtype was graded from 0 to 3 and a mean intensity was calculated.
  
  
  RESULTS
  Eighty percent of PSTT (12/15) were immunoreactive for GPC3 (0, 20; 1+, 20%; 2+, 40%; 3+, 20%) with a mean intensity of 1.3. Stronger, predominately cytoplasmic staining was seen in larger multi- and mononucleated cells with smaller mononucleate cells showing weak muddy cytoplasmic staining. Both PSN cases were positive (1+, 50%; 2+, 50%) and two of nine invasive cervical squamous cell carcinomas showed staining (0, 57%; 1+, 29%; 2+, 14%), predominately in a basal distribution. Other uterine tumors and non-neoplastic tissues were negative.
  
  
  CONCLUSIONS
  Identification of GPC3 in PSTT and PSN is consistent with the derivation of these lesions from intermediate trophoblasts, which have been described to express GPC3. GPC3 may be a useful adjunct immunohistochemical marker in differentiating PSTT from non-trophoblastic tumors.
authors.affiliation: Department of Pathology, The Ohio State University Medical Center, 410 W 10th Ave, 401 Doan Hall, Columbus, OH 43210, USA.
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Ou-Yang
authors.forename: Pei
authors.initials: P
authors.lastname: Hui
authors.forename: Ximing J
authors.initials: XJ
authors.lastname: Yang
authors.forename: Debra L
authors.initials: DL
authors.lastname: Zynger
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D005260:Female; D053673:Glypicans / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D011237:Predictive Value of Tests; D011247:Pregnancy; D011379:Prognosis; D018245:Trophoblastic Tumor, Placental Site / Q000737:chemistry* / Q000473:pathology; D014594:Uterine Neoplasms / Q000737:chemistry* / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; C105937:GPC3 protein, human; D053673:Glypicans