Sacrococcygeal teratoma (SCT) is the most common solid tumor of the neonatal period (incidence: 1/35,000-40,000 live births). It is a germ cell tumor originating from the sacrococcygeal region, from the coccyx tip or presacral area. Contains tissues from all three germ layers (ectoderm, mesoderm, endoderm) — may show cystic, solid, or mixed components. Altman classification has four types: Type I (47%) predominantly external, Type II (34%) external+internal, Type III (9%) predominantly internal with minimal external, Type IV (10%) entirely presacral (internal). Majority are benign (mature teratoma) but malignant transformation (yolk sac tumor, immature teratoma) is possible — malignancy risk increases with age (90% benign in neonatal period, >50% malignant after 2 months). AFP (alpha-fetoprotein) is used as tumor marker. Detected on prenatal US as a presacral mixed cystic-solid mass. MR is preferred for staging and surgical planning. Treatment is surgical resection — coccygectomy is mandatory (recurrence prevention).
Age Range
0-4
Peak Age
-
Gender
Female predominant
Prevalence
Rare
SCT originates from pluripotent germ cells (totipotent stem cells). These cells migrate from Hensen's node (embryological organizer region at the caudal end of the primitive streak). Hensen's node normally disappears after embryological development — abnormal proliferation of remaining pluripotent cells leads to SCT. Tissues from all three germ layers (ectoderm: skin, hair, nerve; mesoderm: muscle, bone, cartilage, fat; endoderm: GI mucosa, respiratory epithelium, thyroid) are found at varying maturity levels. Mature teratoma: well-differentiated, benign. Immature teratoma: poorly differentiated tissues, partial malignant potential. Malignant germ cell tumor (usually yolk sac/endodermal sinus tumor): markedly elevated AFP, aggressive. Mixed cystic-solid appearance on imaging reflects coexistence of different tissue types (fluid, fat, calcification, soft tissue). Cystic components from endodermal secretory structures, solid from mesodermal/ectodermal tissues. Calcifications represent bone/tooth structures, fat density represents dermoid elements.
The signature finding of SCT is a mixed cystic-solid mass in the sacrococcygeal region containing different tissue types from all three germ layers. Coexistence of calcifications (bone/tooth), fat density areas, and fluid-filled cystic spaces confirms teratoma diagnosis. MR shows all components with heterogeneous T1/T2 signal. Altman classification based on external/internal component distribution determines surgical approach.
On US, SCT appears as a mixed cystic-solid mass in the sacrococcygeal region. Cystic components appear as anechoic or low-echogenicity fluid-filled areas, solid components as variable echogenicity soft tissue, calcifications as hyperechoic foci (with acoustic shadow). On prenatal US (usually 2nd trimester), recognized as an exophytic mass extending from the fetal sacral region. In Type I/II, external component is prominent. In Type III/IV, presacral internal component dominates. Color Doppler may show increased vascularity in solid components. Large prenatal SCTs may develop polyhydramnios, fetal hydrops, and placentomegaly.
Report Sentence
A mixed cystic-solid mass measuring ___ × ___ cm is seen in the sacrococcygeal region with calcifications in solid components; findings consistent with sacrococcygeal teratoma.
MRI is the preferred modality for SCT staging and surgical planning. On T2, the mass shows markedly heterogeneous signal: fluid-filled cystic areas are very hyperintense, solid soft tissue intermediate-high signal, fat hyperintense (shows signal loss on fat suppression), calcifications hypointense (signal void). On T1, fat components are hyperintense, fluid hypointense, solid tissue intermediate. MR shows presacral extension, spinal canal relationship, pelvic organ compression, and neural element relationship in detail — critical for surgical planning. Contrast MR shows enhancement of solid components — avid enhancement favors malignancy. DWI may show diffusion restriction in solid malignant components.
Report Sentence
On MRI, a heterogeneous mixed cystic-solid mass measuring ___ × ___ × ___ cm is seen in the sacrococcygeal region containing fat, fluid, calcification, and soft tissue components; presacral extension and spinal canal relationship have been evaluated.
CT shows calcifications (bone/tooth structures — best imaged on CT), fat density (negative HU), and solid soft tissue components within SCT. Calcifications are seen in 50-60% and favor benign teratoma. Fat density (-40 to -120 HU) reflects dermoid elements. Solid components appear at soft tissue density (20-60 HU). Contrast CT shows enhancement of solid components. CT also evaluates bone destruction, vertebral anomalies, and relationship to surrounding structures. However MR is preferred in pediatrics due to radiation concerns.
Report Sentence
On CT, calcifications (bone/tooth structures), fat density areas, and solid soft tissue components are seen in the sacrococcygeal mass; findings consistent with mixed germ cell tumor (teratoma).
On color Doppler US, increased vascularity in SCT solid components raises malignancy suspicion. Mature benign teratoma usually shows low vascularity — few low-velocity flow signals. Malignant component (yolk sac tumor) shows intense neovascularization — low-resistance, high-velocity arterial flow. Prenatally, high-output cardiac failure risk is assessed in large vascular SCTs. Postnatally, Doppler helps determine vascular map before surgery.
Report Sentence
On Doppler US, increased/decreased vascularity is seen in solid components; increased vascularity raises the possibility of malignant component.
DWI diffusion restriction in solid components of SCT suggests malignant transformation. Mature teratoma usually shows no diffusion restriction — ADC values high. Yolk sac tumor or immature teratoma shows diffusion restriction due to high cellularity — hyperintense on DWI, hypointense on ADC map. This finding is important for surgical planning and prognosis — presence of malignant component requires adjuvant chemotherapy.
Report Sentence
Diffusion restriction is seen in solid components on DWI (ADC: ___ × 10⁻³ mm²/s), suggesting possible malignant component.
Criteria
Predominantly external component, minimal presacral extension. 47% of cases.
Distinct Features
Most common type. Easily recognized at birth. Highest benign rate (90%+). Perineal approach resection.
Criteria
External and internal components together, external predominant. 34% of cases.
Distinct Features
External component visible at birth, presacral extension must be evaluated with MR.
Criteria
Predominantly internal (presacral) component, minimal external. 9% of cases.
Distinct Features
Risk of delayed diagnosis. Higher malignancy rate. Combined abdominal-perineal approach may be needed.
Criteria
Entirely presacral (internal), no external component. 10% of cases.
Distinct Features
Highest malignancy risk (50%+). Late diagnosis (infancy/childhood). Usually requires abdominal approach. AFP monitoring critical.
Distinguishing Feature
Meningocele/myelomeningocele is associated with spinal dysraphism — MR shows connection with spinal canal and neural elements. SCT shows no spinal canal connection and contains solid+cystic components with calcification.
Distinguishing Feature
Neuroblastoma elevates catecholamine metabolites (VMA, HVA), calcification pattern different (amorphous, punctate). SCT elevates AFP, calcification in bone/tooth form, fat components present.
Distinguishing Feature
Chordoma typically occurs in adults (40-70 years) with sacral bone destruction. SCT is a neonatal/infant tumor originating from coccyx tip with multiple tissue components.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
3-monthSCT is treated with surgical resection — coccygectomy is mandatory (recurrence rate 35-40% without coccygectomy, <5% with). When diagnosed neonatally, probability of being benign is high (90%+) — early surgery prevents malignant transformation. AFP monitoring is important — physiologically elevated at birth, should normalize by 8-9 months; non-normalizing or rising AFP indicates malignancy. Malignant SCT (yolk sac tumor) is treated with cisplatin-based chemotherapy (PEB). Prognosis: mature benign teratoma — excellent (>95% survival); malignant SCT — >80% survival with chemotherapy. Long-term complications: urinary/fecal incontinence, neurogenic bladder. Follow-up: serial AFP (every 6 months, 3 years), MR for recurrence.
The most common congenital solid tumor of neonates. Early surgical resection (complete excision including coccyx) is curative — leaving the coccyx increases recurrence risk. AFP monitoring is critical for malignant transformation (yolk sac tumor) surveillance. Altman Type IV carries the highest malignancy risk (malignant: Type I 8%, Type IV 38%). Prenatal diagnosis is important for delivery planning: EXIT procedure or cesarean section may be required for large tumors. Hydrops and vascular steal syndrome are causes of fetal mortality. Mature teratoma (grade 0) has the best prognosis; immature components and yolk sac tumor indicate poor prognosis.