title: Primary yolk sac tumor of the urachus.
abstract: BACKGROUND
  Neoplasms originating from the urachus are rare. The most common urachal malignancy is adenocarcinoma, whereas extragonadal germ cell tumors, primarily of the urachus, are an extremely rare finding.
  
  
  OBJECTIVE
  To describe a primary yolk sac tumor (YST) of the urachus in an adult.
  
  
  METHODS
  A 44-year-old woman presented with 6 months of pelvic pain associated with a sensation of progressive mass growth. At the time of tumor resection, the tumor was found to be attached by a pedicle to the dome of the bladder, with no injury to the adjacent organs. Pathological study showed a neoplasm with epithelioid cells, pseudocysts, a myxomatous background, and Schiller-Duval body formations. Immunohistochemistry stains showed positivity to AE1/AE3, α-1-fetoprotein, and α-1-antitrypsin and negativity to other markers.
  
  
  CONCLUSIONS
  An unusual case of a YST in the urachus is presented. This is the first reported adult case based on the authors' bibliographic search.
authors.affiliation: Grupo de Patología del Instituto Nacional de Cancerología INC, Bogotá, Colombia. aromero@cancer.gov.co
authors.forename: Alfredo Ernesto
authors.initials: AE
authors.lastname: Romero-Rojas
authors.forename: Oscar Alberto
authors.initials: OA
authors.lastname: Messa-Botero
authors.forename: Mario Alexander
authors.initials: MA
authors.lastname: Melo-Uribe
authors.forename: Julio Alexander
authors.initials: JA
authors.lastname: Díaz-Pérez
authors.forename: Sandra Isabel
authors.initials: SI
authors.lastname: Chinchilla-Olaya
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D018240:Endodermal Sinus Tumor / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D014497:Urachus / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor