Plicae palmatae in neonates: tumor mimic on sonography.

Plicae palmatae are uterine cervical folds that can be misdiagnosed as a uterine septum on magnetic resonance imaging (MRI). Previous studies in the literature generally tend to include only adults and are limited to MRI findings. Here, we present the case of a 6-day-old girl with a tumorous lesion in her uterine isthmus on sonography. Although we considered uterine tumor as a differential diagnosis, the smooth surface and continuity with a cervical fold on the caudal side suggested that the lesion was, in fact, the tip of plicae palmatae. MRI was subsequently performed, and no restricted diffusion was found, which was useful in ruling out a malignant tumor. Our case highlights that plicae palmatae in neonates can mimic a tumor on sonography. Meticulous observation of a continuity with a cervical fold is essential for correct diagnosis.