Which congenital tumor appears as a mass at the end of the spine near the coccyx and may be detected as a complex pelvic mass in newborns?

• A. Sacrococcygeal teratoma
• B. Wilms tumor
• C. Omphalocele
• D. Gastroschisis

Answer: (A)

Sacrococcygeal teratoma is a congenital tumor that originates at the coccyx, at the end of the spine. In newborns it most often presents as a mass in the sacrococcygeal region, and it can extend into the pelvis or abdomen. Because these tumors can be composed of mixed solid and cystic tissue and may contain vascular components, they often appear as a complex pelvic mass on ultrasound. This combination of location near the coccyx and a complex, multi‑tissue mass in a newborn is classic for sacrococcygeal teratoma.

Wilms tumor is a kidney tumor seen in young children and usually presents as an abdominal mass not tethered to the spinal region. Omphalocele is a midline abdominal wall defect with herniated viscera at the umbilicus, while gastroschisis involves bowel herniation through an abdominal wall defect near the umbilicus; neither characteristically presents as a sacrococcygeal mass.