Sacrococcygeal teratoma

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

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

Presentation varies depending on if a tumour has an intrapelvic location or has an extra-fetal extension (see further classification below). Intrapelvic tumours 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 tumour is composed of the 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 intra-pelvic pre-sacral extension
  • type III: extra-fetal with abdominopelvic extension
  • type IV: tumour 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.

Colour Doppler interrogation in some tumours may show marked hypervascularity with arterio-venous (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

An SCT 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 tumours 5.

General imaging differential considerations include:

For type IV lesions also consider:

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Article information

rID: 8307
Synonyms or Alternate Spellings:
  • Sacro-coccygeal teratoma
  • Sacro-coccygeal teratoma (SCT)
  • Sacro-coccygeal teratoma (SCGT)
  • SCGT
  • Sacrococcygeal teratomas
  • Sacro-coccygeal teratomas

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Cases and figures

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    Figure 1: gross pathology
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    Sacrococcygeal te...
    Case 1: probable type III
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    Case 2: probable type IV
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    Multicystic mass ...
    Case 3: intra-uterine with bilateral hydronephrosis
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    Case 4
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    Case 5
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    Case 6: progressed to IUFD
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    Case 7
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