title: Yolk sac tumor in the abdominal wall of an 18-month-old girl: a case report.
abstract: BACKGROUND
  Pediatric germ cell tumors account for approximately 3.5 % of all childhood cancers for children under the age of 15 years. Up to one-third are extragonadal neoplasms. Germ cell tumors are a heterogeneous group of malignant tumors with a wide variety of histopathological features. Yolk sac tumor is the predominant variant in newborns and younger children. We report for the first time, the presentation of a primary yolk sac tumor in the abdominal wall of a small child.
  
  
  METHODS
  An 18-month-old white girl underwent resection of a small, round subcutaneous lump (1.5×1.3×0.8 cm) of the abdominal wall in her right hypochondriac region. The histopathology was compatible with yolk sac tumor. Her alpha-fetoprotein was initially elevated but normalized after the resection. Magnetic resonance imaging of her abdomen was normal. The surgeon decided to observe and follow her alpha-fetoprotein level closely. One year after resection a local recurrence appeared and her alpha-fetoprotein rose to 58 ng/mL. The surgeon performed a wide resection of the lesion with normalization of her alpha-fetoprotein. Follow-up consisted of measuring alpha-fetoprotein, clinical evaluation, and abdominal ultrasound.
  
  
  CONCLUSIONS
  Clinicians should be aware that a yolk sac tumor can present in an unusual extragonadal place, for example in this case it was subcutaneous. In some cases, conservative treatment can be carried out with careful monitoring of the patient and their alpha-fetoprotein.
authors.affiliation: Department of Pediatrics, ZNA Queen Paola Children's Hospital, Antwerp, Belgium. machielvdakker@gmail.com.|Department of Pediatric Hematology Oncology, UZ Brussel, Jette, Belgium. machielvdakker@gmail.com.
authors.forename: Machiel
authors.identifier: http://orcid.org/0000-0003-2828-6226
authors.initials: M
authors.lastname: van den Akker
authors.affiliation: Department of Pediatric Surgery, ZNA Queen Paola Children's Hospital, Antwerp, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Vervloessem
authors.affiliation: Department of Pediatrics, Heilig Hart Hospital, Lier, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: Huybrechs
authors.affiliation: Department of Pathology, ZNA Middelheim Hospital, Antwerp, Belgium.
authors.forename: Sabine
authors.initials: S
authors.lastname: Declercq
authors.affiliation: Department of Pediatric Hematology Oncology, UZ Brussel, Jette, Belgium.
authors.forename: Jutte
authors.initials: J
authors.lastname: van der Werff Ten Bosch
mesh_terms: D034861:Abdominal Wall / Q000473:pathology*; D014408:Biomarkers, Tumor / Q000032:analysis; D000072700:Conservative Treatment; D018240:Endodermal Sinus Tumor / Q000175:diagnosis / Q000473:pathology*; D005260:Female; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000601:surgery; D014463:Ultrasonography; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D014408:Biomarkers, Tumor; D000509:alpha-Fetoproteins
keywords: Alpha-fetoprotein; Case report; Children; Extragonadal germ cell tumor; Skin tumor; Yolk sac tumor