SACRO - COCCYGEAL TERATOMA: WHAT DO WE EXPECT FROM IMAGING

Souad Maher 1 , Kaoutar Imrani 1 , Valadmir Blata 2 , Siham El Haddad 2 and Latifa Chat 3 . 1. Pediatric Radiology department. 2. Pediatric Hospital Rabat University Hospital Center. 3. Faculty of Medecine and Pharmacy Mohamed V UniversityRabat. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 16 August 2019 Final Accepted: 18 September 2019 Published: October 2019

Sacro-coccygeal teratoma is a germinal tumor containing tissues from two or three embryonic layers (ectoderm, mesoderm and endoderm). Although rare, it remains the most common tumor of the caudal region of the child (7). The etiology of teratomas is not yet clear, but may result from the migration of totipotent cells near the Hensen node in the embryo.
The sacrococcygeal teratoma is considered a surgical emergency because of its potential for malignant transformation from the 4th month of life [4], the prognosis is generally excellent in the neonatal period but gradually becomes darker with advanced age of the child.
In addition to the histological type of the tumor, which is benign in 90% of cases, the other prognostic factors of SCT are: its size as well as its extent, the degree of prematurity and finally the complete resection of the tumor [5,6] . Until recent years, the discovery of SCT was fortuitous at the time of delivery, and they could ask sometimes, depending on their volume, serious obstetric problems.
The antenatal risk of sacro-coccygeal teratoma is that of haemodynamic decompensation that can lead to fetal death in utero or neonatal death (9; 10).

ISSN: 2320-5407
Int. J. Adv. Res. 7(10), 1081-1086 1082 Altman's classification distinguishes four types according to the location and the pelvic extension of the tumor (1,8). Nevertheless, the advent of ultrasound has allowed the antenatal diagnosis of SCT [7], and thus a better obstetric and neonatal management of patients.
For example, ultrasonography and fetal MRI allow prenatal discovery, whereas postnatal imaging determines the importance of an endopelvic component, its impact on neighboring organs and looks for signs of degeneration (1,4,6,7).

Epidemiology
Despite the rarity of SCT, it ranks first among teratomas of the newborn [44]; the 2nd rank of neonatal tumors after lymphangiomas and the 3rd rank of retroperitoneal tumors in children, after neuroblastoma and nephroblastoma [30], with an incidence of about 1: 40,000 and 1: 35,000 live births [2] ]. There is a clear female predominance with a sex ratio of 1/3 to 4 (1,3,7).

Pathology
The sacro-coccygeal teratoma develops from elements of the caudal cell mass that have a potential for multiple differentiation which explains the heterogeneity of the tissues contained in the mass (bone, hair, teeth ...). It is about a tumor reaching preferentially the fetuses of female sex. Malignant degeneration is observed during childhood, so it is essential to surgically remove the tumor before the age of 6 months and completely. Anatomical classification of Altman In 1974, ALTMAN et al [11]. Proposed a topographic classification of sacrococcygeal teratomas in their report to the American Academy of Pediatric Surgey: 1. Type I: Type I teratomas are almost exclusively external with a minimal pelvic component. What are the support of imaging techniques? Antenatal diagnosis Formerly the discovery of SCT was done during delivery, which usually poses serious obstetric problems requiring surgical management which explains the dark perinatal prognosis of these tumors. Advances in ultrasound and fetal medicine currently make it possible to recognize this pathology during pregnancy, but also to specify certain prognostic factors in order to give better information to the couple. The prenatal knowledge of these SCTs also makes it possible to ensure better obstetrical follow-up and, finally, to predict the delivery in a specialized structure where the newborn will be entrusted to the pediatric and surgical team informed, in optimal conditions. Genetic counseling remains useful since family cases have been reported.

Fetal ultrasound (13). It allows:
1. To appreciate the size of the tumor and its dynamic growth. 2. To specify its cystic, solid or mixed nature. 3. Look for calcification, intra-tumoral hemorrhage or necrosis. 4. To appreciate the intra-pelvic extension. 5. To make the differential diagnosis. 6. Look for malformations and associated complications. 7. To evaluate the prognosis and to orient towards the mode and the moment of delivery. 8. Doppler examination makes it possible to appreciate the importance of tumor vascularization

Positive ultrasound diagnosis:
A tumor syndrome with a mass at the distal end of the sacrum, more or less heterogeneous, with mixed contents, with hypo-and hyperechoic zones, irregular borders with cystic components and sometimes calcifications.
Sometimes it is a well-limited tumor with hypoechoic content, sometimes purely cystic in appearance, sometimes heterogeneous mixed component.

Ultrasound classification
According to the classification proposed by the American Academy of Pediatric Surgical Section Survey (AAPSS).

Ultrasound differential diagnosis
The differential diagnosis of sacro-coccygeal teratomas with exclusive endo-pelvic extension will mainly occur in cystic forms, with other intra-abdominal cystic masses: The MRI aspect of the SCT is characteristic, usually a large mass containing well-defined rounded areas of variable intensity signal representing the cystic, solid or calcified components.

Postnatal diagnosis
The clinical presentation of SCT is variable, ranging from a simple induration or wheelbase or asymmetry of the size of the buttock, to a bulky mass that can reach the size of the fetus. Other signs are related to the compression of neighboring organs and degeneration with secondary locations.

Standard radiography:
On the pelvis images, the tumor is in the form of a heterogeneous opacity, multi-lobed, with fuzzy limits. Within this opacity, calcifications or even bone fragments (teeth) may exist.

Ultrasound (13; 16):
Ultrasound: The polymorphism of ultrasound images is related to the nature of the elements that make up the teratoma.

Ultrasound can:
To specify the echo-structure of the mass, it can be liquid, solid or mixed: 1. Fluid echo-structure: the ultrasound shows a rounded mass, of liquid tonality, often multilocular. 2. Solid echo-structure: this is the rarest form. The solid components have an echogenic echo structure, most often inhomogeneous, they may contain calcifications or bone fragments of variable size and shape. 3. Mixed echo-structure: this is the most common form; within an echogenic mass, we find cystic images, well limited, of variable size. Indicate the existence of calcification. 4. Show the presence of hemorrhage, single or multilocular cysts, fatty areas 5. Objectiver intra pelvic extension. 6. Identify the relationship with the bladder, the rectum 7. Explore the urinary shaft for possible bladder dilatation or ureterohydronephrosis. 8. Follow and detect any recurrence MRI allows to characterize the nature of the mass, to specify the links with the muscular and bony structures of the pelvis (the upper strait) and to reveal an intra pelvic extension although the relations with the rectum are less visible than with the scanner.
It is particularly effective for the study of the spine therefore to visualize an intra spinal extension and / or to remove the doubt on a meningocele.

Surgical management:
A SCT, whether diagnosed prenatally or after birth, should benefit from a surgical resection carrying the coccyx in the first days of life, to avoid the risk of malignant transformation that increases with time (2; 5). For degenerate forms or in case of incomplete excision, chemotherapy is coupled with surgery. Technological advances indicate an excision of the in utero mass or an embolization of the tumor vessels by radiofrequency (11; 12). Post-treatment follow-up is clinical and paraclinical with imaging and determination of alpha feto-protein. Monthly monitoring is recommended in the first year, every three months for at least three years, and every year thereafter.

Conclusion: -
Sacrococcygeal teratoma is a rare congenital embryonic tumor with a high potential for malignant transformation and therefore considered a neonatal surgical emergency. Hence the need for antenatal diagnosis and early management. Imaging remains essential for the diagnosis, the evaluation of tumor extension and the search for elements of malignancy. Early surgical treatment prevents progression to malignant transformation.

Conflicts of interest.
The authors do not declare any conflict of interest.

Contributions from The Authors
All authors contributed to this article. All authors have read and approved the final version of the manuscript.