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Sacrococcygeal Teratoma

Sacrococcygeal Teratoma
Section through Mass

Eccentric Sacrococcygeal Teratoma
Sacrococcygeal Teratoma with large cystic components

Findings:

A large predominantly solid mass with cystic components is seen emanating from the sacrum. Numerous small cystic spaces were identified in the mass and color Doppler flow imaging revealed the mass to be quite vascular. Polyhydramnios was seen however, there was no evidence of hydrops fetalis.

Discussion:

Sacrococcygeal teratomas are germ cell tumors that are totipotential and arise from the sacrococcygeal region, usually in the tissues of the developing coccyx. Interestingly enough, the coccyx itself is rarely involved unless the tumor is malignant. Fetal sacrococcygeal teratomas are virtually always benign. The size of sacrococcygeal teratomas varies from 1 to 30 cm with an average mass being 8 cm in size. Neither size nor the prescence of calcification help in differentiating benign from malignant lesions. They are usually recognized externally, however they may extend into the buttocks or pelvis. In 1974 Altman et al classified sacrococcygeal teratomas by location into 4 categories:

Type I

Predominantly external tumors with only a small presacral component

Type II

External tumor mass but with significant intrapelvic extension

Type III

External tumor mass with predominant mass pelvic or abdominal

Type IV

Presacral tumor with no external component

The incidence of sacrococcygeal teratomas is said to be one in 40,000 live births. There is a 4 to 1 female preponderance. There is an increased prevalance of twins in families of patients with sacrococcygeal teratomas. Other congenital malformations are seen in as many as 18% of patients with sacrococcygeal teratomas. Many abnormalities are due to deformation or maldevelopment of adjacent structures due to the large size of the mass. In addition, anomalies have been described in the heart and gastrointestinal tract in these patients.

At sonography, these lesions usually present as a large complex mass extending from the sacrococcygeal area. They tend to be predominantly solid with numerous cystic components. This is often a very vascular lesion, and the large dilated vessels may simulate cystic areas. Color Doppler flow imaging may be helpful in demonstrating the vascularity. Due to the vascular nature of this lesion the fetus may develop hydrops fetalis from high output cardiac failure. This may develop suddenly with subsequent fetal demise. Polyhydramnios is often present. Marked placentomegaly resulting in maternal pre-eclampsia may develop requiring immediate delivery of the fetus. Due to the potential for fetal demise and maternal complications, in utero surgical resection of sacrococcygeal teratomas has been performed in selected cases. Aspiration of a predominantly cystic mass has been reported prior to delivery. Because of the potential for dystocia or hemorrhage from the mass at delivery, cesarean section is often advocated in these cases when the lesion is large.

Differential Diagnosis:

The major differential diagnostic possibilities will depend upon the appearance of the lesion at sonography. Predominantly solid lesions may simulate hemangiomas, lipomas, rhabdomyomas or sarcomas. Lesions that are mostly cystic may simulate meningoceles or myelomeningoceles. Preservation of the posterior elements may help in differentiating these lesions.

References:

Keslar PJ, Buck JL, Suarez ES. Germ cell tumors of sacrococcygeal region: radiologic-pathologic correlation. Radiographics 14:607-620, 1994

Altman RP, Randolph JG, Lilly JR. Sacrococcygeal teratoma: American Academy of Pediatrics surgical section survey-1973. J Pediatr Surg 9:389-398, 1974

Flake AW, Harrision MR, Adzick NS et al. Fetal sacrococcygeal teratoma. J Pediatric Surg 21:563-566,1986

Mintz MC, Minnuti M, Fishman M: Prenatal aspiration of sacrococcygeal teratoma Amer J Roentgenol 141:367-378, 1983

Ein SH, Adeyemi SD, Mancer K: Benign sacrococcygeal teratoma in infants and children: a 25 year review. Ann Surg 191:382-384, 1980

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Peter W. Callen, M.D.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California