Benign neoplasm protruding from the posterior wall of the sacrum and may extend from the abdomen to the pelvis, appearing as a solid or complex mass from the fetal rump?

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

Answer: (A)

A mass that arises from the coccygeal region and protrudes posteriorly from the sacrum, sometimes extending from the abdomen into the pelvis and appearing solid or complex, is characteristic of a sacrococcygeal teratoma. This congenital tumor originates from pluripotent cells near the tailbone and often extends outward toward the fetal rump, which is a key imaging clue on ultrasound. It can present as a externally visible mass or as an internal lesion that has solid and cystic components, and Doppler may show vascular tissue within the tumor.

This diagnosis fits best because the location—posterior sacrum with potential extension along the abdomen into the pelvis—and the appearance as a solid or mixed mass align with sacrococcygeal teratoma. It is the most common congenital tumor and is classically described as arising at the coccyx with posterior extension.

In contrast, a Wilms tumor is a kidney-originating mass seen in older children and would present within the renal area rather than at the sacral posterior region. An omphalocele is an anterior midline abdominal wall defect at the umbilicus with viscera covered by membranes, not a posterior sacral mass. Gastroschisis involves noncovered herniation of bowel through an abdominal wall defect usually to the right of the umbilicus, again not a posterior sacral lesion.