Serous cystadenoma of the ovary: a rare cause of an antenatally detected abdominal cyst.

Antenatally detected cystic abdominal masses in neonates pose a diagnostic challenge, particularly in female infants where ovarian pathology is common but heterogeneous. We report a term female neonate with a large intra-abdominal cyst detected antenatally and persisting postnatally. Imaging revealed a well-defined, unilocular, avascular cyst without solid components, initially suggestive of an enteric duplication cyst. Postnatal imaging was non-specific as to the origin of the lesion. Given the size and persistence of the lesion, surgical exploration was undertaken. Intraoperatively, the mass was found to arise from the right adnexa, and histopathological examination confirmed a serous cystadenoma of the ovary. This rare diagnosis highlights the limitations of imaging in distinguishing benign abdominal cysts from uncommon ovarian neoplasms and underscores the importance of a structured diagnostic approach and timely surgical intervention in selected cases.