2024 Volume 60 Issue 1 Pages 62-67
Neonates presenting with perineal masses are uncommon. In the case of perineal masses, it is difficult to make a diagnosis on the basis of external findings alone, because a variety of diseases can be considered differential diseases. We report a case of perineal mature teratoma in a neonate with a red mucous-membrane-like surface. A 2,438 g female neonate was born at 37 weeks and 4 days without abnormalities on prenatal ultrasonography. She was found to have a multifocal mass in the perianal region after birth and was transferred to our neonatal intensive care unit on the day of birth. The external appearance of the lesion revealed a red mucous-membrane-like surface. A more detailed examination revealed that the mass was localized in the perineal region (between the vagina and the anus). No anorectal malformations were detected as the vaginal, anal, and urethral orifices were confirmed. On the basis of these external findings, rectal prolapse, vaginal polyp, and fetal rhabdomyosarcoma were considered as differential diagnoses. Biopsy results indicated that the mass was a benign tumorous lesion, such as a hamartoma, and not a rectal prolapse. The tumor was resected to confirm the diagnosis. The boundary between the tumor and the surrounding tissues, such as those of the vaginal wall, rectal wall, or anal sphincter muscles, was relatively clear during tumor resection. The mass was dissected completely without injuring the surrounding organs. The tumor was covered with a stratified squamous epithelium and was pathologically diagnosed as a mature teratoma. A mucosal-like appearance may be present in masses arising under the stratified squamous epithelium in the perineal lesion.
