Sacro-coccygeal teratoma (SCT) refers to a teratoma arising in the sacro-coccygeal region. The coccyx is almost always involved 6.
Demographics and clinical presentation
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 a M:F ratio of 1:4. Sacrococcygeal region is the commonest location for non CNS teratomas.
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. There are most often mixed solid/cystic, although purely cystic types can occur in ~15% of cases.
The 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 feto protein (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 abdomino-pelvic extension
- type IV: tumour developing completely 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 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 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 artifact because of calcifications
- T1 C+ (Gd): enhancing solid components
- high output cardiac failure from AV shunting: which in turn can cause hydrops fetalis
- ureteric obstruction
- gastro-intestinal tract obstruction
- compression of underlying nerves: giving urinary/faecal incontinence
- tumour rupture
Treatment and prognosis
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 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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- 2. Danzer E, Hubbard AM, Hedrick HL et-al. Diagnosis and characterization of fetal sacrococcygeal teratoma with prenatal MRI. AJR Am J Roentgenol. 2006;187 (4): W350-6. doi:10.2214/AJR.05.0152 - Pubmed citation
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- 8. Hogge WA, Thiagarajah S, Barber VG et-al. Cystic sacrococcygeal teratoma: ultrasound diagnosis and perinatal management. J Ultrasound Med. 1987;6 (12): 707-10. J Ultrasound Med (citation) - Pubmed citation
- 9. Yu JA, Sohaey R, Kennedy AM et-al. Terminal myelocystocele and sacrococcygeal teratoma: a comparison of fetal ultrasound presentation and perinatal risk. AJNR Am J Neuroradiol. 28 (6): 1058-60. doi:10.3174/ajnr.A0502 - Pubmed citation
- 10. Batukan C, Ozgun MT, Basbug M. First trimester diagnosis of sacrococcygeal teratoma using two- and three-dimensional ultrasound. J Clin Ultrasound. 39 (3): 160-3. doi:10.1002/jcu.20791 - Pubmed citation
- 11. Roman AS, Monteagudo A, Timor-tritsch I et-al. First-trimester diagnosis of sacrococcygeal teratoma: the role of three-dimensional ultrasound. Ultrasound Obstet Gynecol. 2004;23 (6): 612-4. doi:10.1002/uog.1055 - Pubmed citation
- 12. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon