Atypical epithelioid trophoblastic lesion presenting as pseudocyst from the niche in the cesarean scar: A case report and review of the literature.

OBJECTIVES

In 2020, the WHO introduced Atypical Placental Site Nodule (APSN) into the new classification of female genital tract tumors, describing it as an intermediate lesion between placental site nodule (PSN) and epithelioid trophoblastic tumor (ETT). Unlike APSN which is typically a nodule, we present a case of a post Cesarean Section (CS) cyst and fistula formation with intermediate pathologic features between PSN and ETT. This type of lesion has earlier been described as "atypical epithelioid trophoblastic lesion". We aim to review similar cases in the literature to gather data on clinic, sonographic and histopathological characteristics.

STUDY DESIGN

We conducted a search on PubMed and Web of Science databases. Given the novelty of the term atypical epithelioid trophoblastic lesion and its lack of validation, we broadened our search to the term 'APSN' including similar cases with unique clinicopathologic features, specifically those involving cyst and fistula formation after CS. Two reviewers independently screened articles and extracted relevant data.

RESULTS

We describe a case of atypical epithelioid trophoblastic lesion presenting as a cystic lesion anterior to a cesarean scar niche. We found eight similar cases in literature. All presented with a cyst and/or fistula that occurred several months, or even years, after CS. Symptoms were vaginal bleeding (2), abdominal pain (2), hematuria (1), amenorrhea (3) and urinary frequency (1). Ki-67 proliferation indices exceeded 12 % in 4/8 (50 %) cases. Necrosis or mitotic figures were not observed in 7/8 (87.5 %) cases. No case displayed signs of recurrence during follow-up (range: 1-12 months).

CONCLUSION

There are only eight cases in literature that display similar sonographic and histopathological features to the case of atypical epithelioid trophoblastic lesion we presented. Further molecular studies focusing on the gene signature of the lesion and gathered data from gestational trophoblastic disease registries could contribute to a better understanding of the origin and behavior of this specific intermediate lesion.