Congenital lesions are embryologic remnant which has been present from the birth. They account 55% to 75% of all presacral lesions with subgroups of developmental cysts, chordomas, anterior sacral meningoceles, rectal duplications and adrenal rest tumors[1].

Developmental cysts: About 60% of congenital RTs are developmental cysts originating from different embryologic origin. There is 1:2 female predominance[13]. This predilection may be the result of more frequent routine rectal or pelvic examination in female population than males which makes females more likely for diagnosis[14]. Depending on the origin of embryonic cell, they can be epidermoid, dermoid, tail gut cyst or teratomas. Epidermoid and dermoid cysts are derived from ectodermal tube closure defect. Dermoid cysts made up with more matured components and comprise dermal appendages like hair follicles and sweat glands whereas epidermoid cysts have squamous epithelial lying (Figure 3). Women in between 4^th or 5^th decades are more prone to develop dermoid and epidermoid cysts. These cysts likely contain viscid green-yellow material unless infected[15]. The next and less frequent congenital lesion sometimes referred as cystic hamartoma is tail gut cysts. Glandular, mucous producing columnar epithelium in these cysts explains it’s derivation from tail gut remnants. Although cyst wall may contain scattered bundles of smooth muscle fibers, muscular and serosal coat is not present. Malignant degeneration is rare in tail gut cysts.

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Figure 3 Macroscopic appearance of dermoid cyst (A), epithelial inclusion cyst (B) and schwannoma (C).

Teratomas: Even sacrococcyx is the most common location for teratomas in neonates, it is rare in adults. Teratomas, which have 5% to 10% malignant potential can give rise to multiple solid or cystic lesions containing various tissue types like respiratory, nervous and gastrointestinal system epithelium[16]. Nearly 30% of resected adult teratoma specimens harbor malignancy. The one tip to predict whether it is benign or malign is relation to adjacent structure. The tendency of malignant teratomas to adhere coccyx, rectum and other visceral organs is not seen in benign lesions.

Chordomas: Chordoma is the most common malignant and the most extensively studied RT. It is the second most common RT in RS occurring in three of seven patients[17]. Even one-third occurs in RS, they can be found anywhere in vertebral column[18]. Slow growing nature of chordoma postpones the diagnosis until 40 to 60 years of ages[1]. Long standing vague pain and symptoms associated with nerve compression like incontinence or impotence are frequent presentations. These frequently lobulated, gelatinous masses that attack and break down the neighboring structures need complete resection in order to prevent recurrence. The typical radiological finding for chordoma is “Fang” sign, the finding of sacral bone destruction. Recurrence rate is as high as 44% and because these recurrences are locally aggressive, patients should be warned for probable postoperative sequelae from minor urinary incontinence to paralysis[19]. Chordomas are more common in males with an expected male/female ratio of 2:1[14].

Anterior sacral meningocele: Anterior sacral meningocele is the third group of congenital RT. It is a dural hernial sac containing cerebrospinal fluid as a continuation of subdural space from a defect in the sacrum. Dural connection causes increase in cerebrospinal fluid pressure during straining or defecation. Anterior sacral meningoceles are more common in females and can present with recurrent meningitis[10].

Miscellaneous: The last category of congenital RT is adrenal rest tumors and rectal duplications. The latter can contain mucosa with crypts and villi, smooth muscle and serosa components of intestine because they are remnants of duplicated rectum. Adrenal rests tumors are very sporadic and must be managed like an ectopic pheochromocytoma.

Inflammatory RTs are less common than congenital ones. They may be residues of foreign bodies of any kind. Tuberculosis, granulomatous disorders, perianal abscess, diverticulitis resulting pelvic abscess and fistulas can cause chronic inflammatory masses in the RS.

Neurogenic tumors tend to be large and account 10% of RTs. This category includes neurofibromas, neurolemmomas, ependymomas, ganglioneuromas, and neurofibrosarcomas. Even benign lesions constitutes two thirds of neurogenic RTs, severe neurological sequelae can be seen if these lesions are originated from the spinal cord. Neurogenic and osseous RT can be benign or malignant. Benign ones often require complete resection but recurrence rate is high in osseous lesions.

The last but not least group of RT constitutes masses such as metastatic disease from rectum, sarcomas, malignant fibrous histiocytomas, lymphangiomas, lymphomas, fibrosarcomas, liposarcomas, hemangiomas and others that can be found anywhere else in the retroperitoneum[8]. They constitute 10% to 25% of all RTs[1].

However these classifications do not consider the location of RT in the RS which is important determinant for operative and pathologic considerations. A suggestion of a classification system based on the tumor emplacement to facilitate surgical strategy and postoperative sequelae prospection (Figure 4)[20]. According to this classification, type 1 refers to RTs without any connection to the sacrum. Type 1 RT is at the coccyx level (below S3) and separate from the bony trunk of sacrococcyx. It can easily be separated from surrounding structures and removal is not difficult[2]. Type 2 RT is also settles with the same level as type 1 but has connection with the coccyx and/or sacrum. Their surgical resection promise no neurologic deficit[12]. Type 3 RT requires a unilateral resection of the sacral nerve(s), probably resulting fecal and/or urinary incontinence because type 3 RT involves the sacrum at or above the S3 nerve root unilaterally. Type 4 RT has large communication with the sacrum at or above S3 bilaterally in which permanent sphincter deficit is almost unavoidable.

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Figure 4 Classification of retrorectal space depending on its relationship with the sacrum (Losanoff et al[20]).

Further division of these four types is A; resection of the adjacent sacral soft tissue and bone is mandatory without adjacent organs and B; resection of organs such as rectum, bladder is obligatory.

Anterior approach is suitable for tumors at higher location having the lowest border above the 4^th sacral bone. Absence of sacral involvement is essential for this approach. This kind of surgery has advantages of good disclosure of adjacent pelvic structures such as iliac vessels and ureters (Figure 5). Throughout the abdominal approach, rectum is first isolated and separated from resection area and after ligation of middle sacral and internal iliac vasculatures, presacral fascia is dissected. Surgeon should be in great care during tumor excision for presacral hemorrhage because the middle sacral blood vessels and the presacral venous plexus are in this region. Possible perineal necrosis can be prevented by preservation inferior gluteal artery which is terminal branch of anterior division of the internal iliac artery. The main cause of intraoperative death is hemorrhage of the presacral venous plexus. Traditional hemostasis methods may not be enough and troublesome bleedings can be overwhelmed by some challenging preventive measurements such as temporary gauze tamponade, bone wax or breast size implanter[24].

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Figure 5 Laparotomy for retrorectal space. Iliac vessels and RS can easily be reached after lateralization of rectum. IV: Iliac vessels; RS: Retrorectal Space; R: Rectum.

This procedure is suitable for low lying tumors which are not extending beyond 4^th sacral element. Usual length of a finger can extend up to 4^th sacrum. If the proximal end of the tumor is felt by digital sensation, this means that there is no extension beyond that point. The patient is positioned in a prone jack-knife position, preferably buttocks are separated apart (Figure 6). A transverse incision overlying the coccyx offers good disclosure of the retrorectal space especially in case of nerve involvement. A longitudinal incision may be used alternatively on the lower sacrum to the level of anoderm while taking care for not to cause any injury to external sphincter. After dividing the subcutaneous fat, the levator muscles and the anococcygeal ligament lying deep to the lumbosacral fascia are exposed. Transection of anococcygeal ligament allows mobilization of the coccyx. Coccyx can be transected to provide sufficient exposure for dissection, the gluteal muscle may be separated, and sacrectomy of S4-S5 can be achieved afterwards. Separation of the plane between the tumor and the mesorectum will be easy. The major disadvantages of posterior approach are injury to the lateral pelvic nerves and absence of control over pelvic vessels. While comparing with anterior or combined procedures, probable hemorrhage can be lowered by posterior method[25]. If the lesion is benign, there should be an identifiable fat plane between the mesorectum and RT provided that there was no infection before. In case of cystic and/or small lesion, the surgeon can place the nondominant hand index finger with double-glove in the anal canal and lower rectum and then depress the tumor through the incision. Undesired injury to the rectal wall during the dissection can also be prevented with this manner. The posterior approach is embraced of different techniques such as transsphincteric, transsacral, transrectal, transanorectal, and transsacrococcygeal approaches. Every one of these techniques has its own losses and benefits and can be chosen based on the characteristics and site of the tumor and the surgeon’s preferences.

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Figure 6 Excision of cystic lesion located low level in retrorectal space by using posterior approach.

Ruptured transrectal cysts and solid but well delineated lesions extending rectal muscular layer with suitable level should be subjected to this kind of surgical approach. A modification of this approach is intersphincteric resection of RT which starts with retrorectal space access via intersphincteric plane or a transvaginal incision, when the tumor is low enough and not in the midline, lying between vaginal wall and rectal muscularis layer. Anal sphincter damage confronts us during the above incisions but one can avoid the possibility of sacral nerve injury, postoperative urinary retention and unintentional rectal perforation with these cuttings.

This procedure is suitable for the tumor extending both vertical sides of the 4^th sacral vertebra. Operation begins with the patient in modified lithotomy position and entering the retroperitoneal space through the areolar plane between the mesorectum and the presacral fascia, to gain access for dissection of the upper part of the lesion. While going down to the deep pelvis, identification of planes between the tumor and surrounding tissues will become more difficult, than patient may be repositioned in the jack-knife position for the perineal phase of the procedure. An incision is then made over the sacrum and coccyx through the anus, while being awake not to damage external sphincter. Division of anococcygeal ligament and retraction of levators can be done afterwards. The gluteus maximus muscles are then retracted away and the sacrospinous, sacrotuberous ligaments, and piriformis muscles are divided bilaterally to delineate the sciatic nerve. Any dural openings should be closed to prevent cerebrospinal fluid leakage or infection. One S3 nerve should be preserved to maintain proper fecal and urinary function. Colostomy should be matured if unilateral preservation of the S3 is not possible. In case of benign or have a low relapse probability, colonic continuation can be achieved with anastomosis but diverting ileostomy should be considered.

Major advantages of this approach appear when infection or inflammation cause disappearance of the dissection planes or exposure of the neighboring structures like rectum, ureters, iliac vessels as well as nerve roots are obligatory. This is a case in chordoma in which partial sacral excision extending above S-3 is necessary. Complete and one piece tumor excision with a hemisacrectomy can be accomplished after exposure of the sacrum through the posterior approach. Bone allograft, iliosacral screws, and Galveston type fixation are necessary for lumbopelvic stabilization as bony reconstruction after the end of tumor resection[26]. Transpelvic vertical rectus abdominis myocutaneous flap reduces wound complications[27]. In case of anterior sacral meningocele, reverse abdominoperineal approach is the operation of choice because the communications can easily be recognized by posterior approach, and then conveniently sutured at the anterior phase.

Nearby location of the RT to the rectum and the anal canal necessitate good bowel preparation before surgery. Ureteral catheter should be placed to feel and protect the ureters if indicated. Successful resection for highly vascular lesions or for reduction of blood loss during surgery can be facilitated with transcatheter arterial embolization of tumors. Beside of decreased blood loss and more clear surgical vision, possible elimination for the need of anterior approach, and R₀ resection of the sacral chordoma will be pleasing[28].

While planning the surgery, coccyx resection consideration is important. Routine resection of the coccyx this is mandatory if the coccyx is free of malignancy the histopathology is not clear. Local recurrence rate rise up to 25% to 56% if RT resection is not achieved with coccyx resection by transsacral approach[29].

Radical surgeries such as total sacrectomy in case of first sacral bone involvement has been tried out but structural and neurologic sequels are very high[20]. Postoperative neurogenic bladder rate up to 15% and fecal incontinence at a rate of 7% cause severe social life problems[21]. Immolation of sacral nerves bilaterally creates this problem in almost always every cases but unilateral sacrification can give a chance to preserve these functions well[30]. Normal continence and defecation can be protected not only with conservation of S-1 and S-2 bilaterally but also at least one S-3 nerve root is required to protect normal bowel and anorectal function[8]. Urinary and fecal incontinence and impotence in males are almost inevitable after sacrification of S2-S4 nerve roots at both side. Bilateral S2 root preservation leads to mild and reversible bladder sphincter dysfunction which responds to rehabilitative treatment in certain extend.

Laparoscopic approach is reported to be feasible and safe. Surgical trauma reduction, better visualization of the deep structures in the presacral space and less vascular and neurological injuries are benefits of laparoscopy[31]. There is a case of RT operated with the help of robotic device. Beside of the known benefits of laparoscopy, such as pain, scar, hospital stay reduction, the greatest advantage of a robotic approach to the PS is improving surgical technique to allow retraction and handiness provided by the instruments in this confined area. Longer operative time and high cost are two potential disadvantages of the robotic technology expected to be overcome[32].

Demonstration of the efficacy of adjuvant treatment in rare and heterogeneous disease of RTs is difficult. Even though it has a minimal role in management of RTs, adjuvant chemoradiotherapies have been tried in some surgically unresectable lesions. Chordomas are the most aggressive and radiation resistant tumor at this location but high dose radiation therapy has been tried[33]. Radiation of the affected area with neutrons by high linear energy transfer therapy or charged particle carbon ion radiotherapy (CIRT) in inoperable and recurrent chordomas was able to show 54% local control rate[34]. After 3 years follow up, conventional radiotherapy and CIRT demonstrated 35% and 73% control rates respectively. Big radiosensitive tumors can be decreased in size and this can help to preserve vital elements of the pelvic region. Direct radiation to smaller field also decreases the patient morbidity[35]. However long-term response to this therapy is doubtful.

Inhibitor of epidermal growth factor receptor’s tyrosine kinase domain, such as Imatinib, Cetuximab, gefitinib has been shown to be effective in the management of recurrent and metastatic chordoma[36,37]. Proceedings with Imatinib chemotherapy have helped to increase progression-free survival in advanced chordomas cases[22]. Some RTs such as Ewing sarcoma, osteogenic sarcoma, neurofibrosarcomas, and desmoid tumors necessitate neoadjuvant therapy.