Prenatal Diagnosis of a Fetal Spinal Malignant Small Round Cell Tumor: Ultrasound, Fetal MRI, and Immunohistochemical Findings.

Fetal tumors are extremely rare, but with more widespread ultrasound screening in pregnancy, the incidence of prenatal diagnosis is increasing. The perinatal tumor concept refers to the tumors diagnosed either prenatally or within the first month after birth. This is a case report of a fetal spinal malignant tumor. On prenatal ultrasound, a closed neural tube defect was suspected at first glance because of a paraspinal soft tissue mass connected to the spinal canal and tethered spinal cord at 22 weeks of gestation. Fetal magnetic resonance imaging performed at 30 weeks of gestation revealed a spinal cord mass extending from the coccyx to the thoracic vertebrae, with involvement of the paraspinal soft tissues and the abdominal cavity. Due to its poor prognosis, the pregnancy was terminated, and postnatal excisional biopsy and pathological examination made the final diagnosis of a malignant small round cell tumor.