Extragonadal teratomas in women and adolescent girls: A systematic review.

INTRODUCTION: Extragonadal teratomas (EGTs) are rare and the commonest intra-abdominal subtype is omental. We present two cases: 1) a parasitic omental teratoma likely secondary to auto-amputation of an ovarian teratoma with subsequent omental reimplantation and 2) an omental immature teratoma likely due to parthenogenetic activation of displaced primordial germ cells. We subsequently conduct a systematic review to characterise EGTs.

METHODS: We sourced for English, peer-reviewed case reports of extragonadal teratomas in women and female adolescents aged 11 and above published from inception of each database through 31st June 2020 following PRISMA guidelines. Two authors reviewed each case for appropriateness and each case was graded for methodological quality utilising a modified Newcastle Ottawa Scale. PROSPERO Registration Number: CRD42020190131 RESULTS: Upon literature review between 1920-2020, from an initial screen of 818 articles, 67 articles were selected featuring 70 cases. One case featured an immature teratoma while the remaining were mature. Omental EGTs were the most common (56.5 %) followed by Pouch of Douglas and uterosacral ligament (23.2 %) and upper abdomen (14.5 %). There were statistically significant differences in EGT mean sizes between each location with the largest being in the upper abdomen (10.9 cm) and the smallest being in the adnexa or hernia (6.2 cm). Auto-amputation was deemed the commonest cause amongst omental EGTs (55.3 %) and Pouch of Douglas and uterosacral ligament EGTs (37.5 %) while 70 % of upper abdominal EGTs were likely due to displaced primordial germ cells. We characterise clinical features associated with each pathogenic mechanism and imaging characteristics of EGTs. Characterisation of EGT tumour marker profiles was limited as only 42.9 % of cases reported them but 19.2-25.0 % had raised tumour markers. The main risks are torsion, rupture, immature components and potential malignant change of the cell lines. Treatment is largely surgical. The mean size of EGTs approached laparoscopically and via laparotomy was 5.23 cm and 9.16 cm respectively.

CONCLUSIONS: While rare, EGTs should be considered when evaluating pelviabdominal masses with imaging characteristics consistent with teratomas. Confirmation is usually intraoperative and a laparoscopic approach is reasonable if there is good surgeon comfort and the size is about 5 cm.