Developmental tumors: tailgut cyst (cystic mucinous hamartoma), teratoma, rectal duplication, epidermoid cyst, dermoid cyst
Anterior sacral meningocele
Lipoma, leiomyoma, desmoid tumor
29.2.1 Congenital Tumors
Congenital tumors are the most common RRT: 79 of every 120 (66 %), in the experience of the Mayo Clinic . The classification described by Malafosse et al.  in 1977, then reviewed and corrected by Barthod et al.  in 1996, is used by the majority of authors:
Vestigial tumors: cystic (epidermoid, dermoid, enteroid; e.g., hamartomas or rectal duplications) and noncystic (teratomas)
Nonvestigial tumors: chordomas, hemangiomas
220.127.116.11 Vestigial Tumors
Dermoid and epidermoid cysts
Dermoid and epidermoid cysts (Fig. 29.1a) are typically benign and are frequently observed in women aged 40–50 years. The main risk is infection (30%) and can then be difficult to distinguish from peri rectal abscess. Epidermoid and dermoid cysts tend to be well circumscribed, with a thin outer layer. They contain stratified squamous cells and skin appendages [8, 11]. Unlike tailgut cysts, they do not contain transitional or glandular epithelium. They are usually unilocular, filled with a clear liquid.
Epidermoid cyst on T1 axial and T2 sagittal sections on magnetic resonance imaging
Enteroid (tailgut) cysts
Retrorectal hamartomas (tailgut cysts) or mucoepidermoid cysts (Fig. 29.2) are the most common cysts derived from endoderm and mesoderm. They are embryonic remnants of the terminal portion of the primitive hindgut, located after the cloacal membrane (tailgut). The distal portion of the primitive hindgut is temporary and should fully regress at the seventh week of gestation. Failure to regress is one origin of tailgut cysts. The second possible source of a hamartoma is persistence of the neurenteric canal, which is formed from the union of the endoderm and mesoderm. This canal is formed the 19th day of gestation and is obliterated when the caudal part of the notochord is completely formed. Persistence of this canal can be observed above the S2–S3 vertebrae in adults and may be the source of a congenital cyst. Histologically, the wall of these cysts can form from one or multiple types of epithelium normally found in the gastrointestinal tract of adults and fetuses . These cysts are defined by the presence of at least transitional cells or cylindrical epithelium. Squamous epithelium is present in 75 % of cases, possibly as a result of metaplasia induced by inflammation [10, 11].
Tailgut cyst onT1 and T2 axial sections on magnetic resonance imaging
Enteric cysts occur predominantly in middle-aged woman and present with pain (often during defecation) or symptoms related to a mass in 50 % of cases. Rectal exam may identify an extrinsic mobile or fixed fluctuating lesion. The location is predominantly in retrorectal space, although tailgut cysts have been described in the perianal space, the buttocks, the postsacral space, and even anterior to the rectum. Macroscopically, most have multicystic locules (80 %) and are well circumscribed but unencapsulated, usually starting in the retrorectal space. They rarely reach the rectal wall. The cysts can contain amorphous debris, keratin, or mucus (in the presence of mucus-secreting cells). Unlike teratomas, no calcifications are found. Inflammation is often present, whether acute or chronic (especially after trauma with cyst rupture), but it does not correlate with clinical symptoms. Malignancy is possible, in the form of adenocarcinoma or squamous cell carcinoma (occurs in 7 % of enteric cysts) . Various findings are usually seen on magnetic resonance imaging (MRI):
Median lesion in the retrorectal space, with possible forward and lateral development
Multilocular cyst and the presence of variably sized satellite cysts
Wall that is often visible, which can be enhanced with gadolinium
Varied signal: homogeneous, either a hyper signal relative to T1 and T2, or either an iso signal T1 and hyper or iso signal T2
Tailgut cysts differ from duplication cysts in that they do not have a well-defined muscular wall, myenteric plexus, or serosa, although smooth muscle fibers can be found in a single layer.
Duplication cysts can occur throughout the digestive tract, with a predilection for the small bowel. Cystic rectal duplication represents 5 % of all developmental cysts. They occur solely or in combination with different abnormalities (lumbosacral, urogenital, and/or digestive). They can present either as a cyst (90–95 %) or a secondary bowel parallel to the normal digestive tract. Only the mesenteric edge of the duplication is in close contact with the main digestive wall. In 80 % of cases, however, the lumen does not communicate with the primary gastrointestinal tract (noncommunicating duplications). Retrorectal duplication cysts are usually not communicating. They must have two smooth muscular layers and a mucosa that is similar to the rectal mucosa, and they sometimes contain ectopic tissue (e.g., gastric mucosa in 25 %, pancreatic tissue). Malignant transformation has been described .
Teratomas are the most common tumors in children. These are diagnosed in half of cases during the antenatal period using ultrasonography. Teratomas are characterized by a combination of differentiated tissues derived from the three germ layers: ectoderm (squamous and pilosebaceous annexes, brain and nervous tissue, glia, retina, and choroid plexus ganglion), endoderm (mucous, gastrointestinal, and lung, thyroid, salivary glands), and mesoderm (bone, cartilage, smooth muscle, fibrous and fatty tissue) [8, 12, 13]. They can become malignant (10 %), forming teratocarcinomas, choriocarcinomas, and dysgerminomas .
18.104.22.168 Nonvestigial Tumors
Chordomas are the most common malignancies of the retrorectal space [1, 15–18]. They develop from embryonic remnants of the notochord. Fifty to 60 % of chordomas are located in the sacrococcygeal region, but they can be located all along the spine. These tumors are rare (2–4 % of malignant bone tumors), frequently diagnosed in patients between 40 and 70 years old, and are more common among males (male-to-female ratio, 2:1). These tumors have a low possibility for malignancy, with approximately 20 % metastatic risk, but they can be very aggressive locally. They grow slowly and often are fortuitously discovered during a routine rectal or pelvic exam. Chordomas are lobulated gelatinous masses that invade and destroy adjacent bone structures, requiring radical resection to prevent recurrence. Computed tomography (CT) can show a large osteolytic soft-tissue mass in the sacrum and allow evaluation of the locoregional invasion. MRI characterizes this tumor with a hypo signal or intermediate signal in T1 and an hypersignal in Fig. 29.3. Enhancement of the tissue component varies but is often moderate. Their prognosis is poor, and important sequelae occur after surgical resection according to the level of the bone and sacral nerve resection.
Sacral chordoma on T1 and T2 sagittal sections on magnetic resonance imaging
Meningoceles are rare, sporadic, and more common in women than men. The anterior sacral meningocele is the result of a herniated dural sac in the presacral space, caused by a bony defect of the anterior wall of the sacrum. The sac communicates with the spinal canal and is filled with cerebrospinal fluid. Patients can present with headache exacerbated by defecation, urinary symptoms, constipation, sacral pain, and sometimes meningitis. Other bone defects occur in 50 % of cases. CT reveals a well-circumscribed tumor and a watery, uniform cyst and confirms the bone defect.
29.2.2 Neurogenic and Bone Tumors
Neurogenic and bone tumors each represent approximately 10 % of RRTs.
22.214.171.124 Neurogenic Tumors
The main neurogenic tumors are mostly benign: solitary neurofibromas, schwannomas, and ganglioneuromas. Presacral plexiform neurofibromas can be part of the lesions observed in Recklinghausen type 1 disease. Malignant transformation is rare but can occur in 8–10 %. Surveillance with MRI is usually advised.
Schwannomas develop at the expense of the Schwann cells of the sacral nerve roots. They are rarely located in the presacrum. These are slow-growing tumors and are usually discovered fortuitously. Schwannomas are mainly solitary but can be part of neurofibromatosis type 1 in 5–15 %. Malignancy is rare. CT shows a well-demarcated oval or spherical mass with sharp contours in the presacral space. Cystic alterations or intratumoral calcifications are possible. A schwannoma can present as an extension through a foramen that seems enlarged. On MRI, the tumor is typically hypointense in T1, hyperintense in T2, and takes contrast. The signal may be heterogeneous in the case of a calcification or the presence of a cyst.
126.96.36.199 Bone Tumors
The most common bone tumors are benign giant-cell tumors characterized by hypervascularization and local aggressiveness. Malignant tumors include mainly sarcomas  and, especially in children, osteochondrosarcoma, chondrosarcoma, and Ewing sarcoma. Because of their relatively rapid growth, these tumors often reach a considerable size. The lungs are the preferential sites of metastasis.
29.2.3 Mixed Tumors
Gastrointestinal stromal tumors, liposarcomas, extraabdominal desmoid tumors, adenocarcinomas, fibrosarcomas, and hemangiomas represent various mixed tumors. Fibromatosis (desmoid tumor) is also part of this mixed-tumor classification. The natural history varies from spontaneous regression to aggressive growth. The treatment objective for these lesions is not to resect at all costs but to stabilize the lesion.
The incidence of RRT is difficult to estimate because only small population a few articles with low numbers have been reported [2–5]. A general surgeon practicing outside a specialized center can expect to see just one RRT throughout his or her entire career. Table 29.2 summarizes the results of the main studies of RRTs.
Results of the main studies of retrorectal tumors
Malignant tumors, n (%)
Kraske procedure/abdominal approach/Kraske and abdominal mixed
Morbidity, n (%)
Grandjean, 2008 
6 (20 )
Gao, 2011 
6 (17 )
8 (22 )
Glasgow, 2005 
8 (24 )
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