Sacrococcygeal teratoma

Last revised by Subhan Iqbal on 22 Dec 2022

Sacrococcygeal teratoma refers to a teratoma arising in the sacrococcygeal region. The coccyx is almost always involved 6.

It is the most commonest congenital tumor in fetus 11 and neonate 3. The incidence is estimated at ~1:35000-40000. There is recognized female predilection with an M: F ratio of 1:4. The sacrococcygeal region is the commonest location for non-CNS teratomas.

Presentation varies depending on if a tumor has an intrapelvic location or has an extra-fetal extension (see further classification below). Intrapelvic tumors can manifest after birth with genitourinary and gastrointestinal symptoms given the compression of those structures. 

They are thought to arise from totipotent cells from the node of Hensen 1,3 at the anterior aspect of the coccyx by about the 2nd to 3rd weeks of gestation. They are most often mixed solid/cystic, although purely cystic types can occur in ~15% of cases.

A tumor is composed of all three germ cells (i.e. ectoderm, mesoderm and endoderm).

  • most cases tend to be sporadic 12

Can have elevated levels of:

  • alpha-fetoprotein (AFP)

  • beta HCG

A pathology-based classification is as:

  • benign (mature): much more common, comprising ~ 60-70%

  • malignant (immature)

A location-based classification system according to the American Academy of Pediatric Surgery Section Survey is:

  • type I: developing only outside the fetus (can have small pre-sacral component); accounts for the majority of cases, 47% 12

  • type II: extra-fetal with intrapelvic presacral extension

  • type III: extra-fetal with extension through the pelvis into the abdomen

  • type IV: tumor developing entirely in the fetal pelvis

  • may show a large mass projecting from the lower pelvic region or within the abdominopelvic cavity

  • may show calcification

Not part of a routine investigation. Identifies bone, fat and cystic components. Calcification may again be seen.

Mature types tend to be more cystic which show as anechoic components. Solid types (which are much rarer) often show an echogenic mass within the pelvis.

The correlation between sonographic appearances and malignant components are thought to be poor 7.

Color Doppler interrogation in some tumors may show marked hypervascularity with arteriovenous (AV) shunting.

Superior to ultrasound especially in the assessment of the following areas 2:

  • colonic displacement

  • ureteric dilatation

  • associated hip dislocation

  • intraspinal extension

  • vaginal dilatation

  • metastatic assessment in malignant lesions

Signal characteristics can significantly vary depending on the constituent of the teratoma 1.

  • T1: fat components appear high signal, calcific/bony components low signal

  • T2: fluid (cystic) components appear high signal, calcific bony components low signal

  • T2* GRE: magnetic susceptibility artefact because of calcifications

  • T1 C+ (Gd): enhancing solid components

A sacrococcygeal teratoma can be benign or malignant depending on whether mature or immature. The majority, however, tend to be benign (~80% 11). Those presenting in older infants tend to have a higher malignant potential which those presenting in utero have a poor prognosis due to complications. Malignant change may be also commoner in males. Treatment is with surgical excision inclusive of coccygectomy with additional chemotherapy for malignant tumors 5.

General imaging differential considerations include:

For type IV lesions also consider:

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Figure 1: gross pathology
    Drag here to reorder.
  • Case 1: probable type III
    Drag here to reorder.
  • Case 2: probable type IV
    Drag here to reorder.
  • Case 3: Sacrococcygeal teratoma
    Drag here to reorder.
  • Case 4
    Drag here to reorder.
  • Case 5
    Drag here to reorder.
  • Case 6: progressed to IUFD
    Drag here to reorder.
  • Case 7
    Drag here to reorder.
  • Case 8: sacrococcygeal teratoma
    Drag here to reorder.
  • Case 9: immature
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.