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Tailgut Cyst (Retrorectal Cystic Hamartoma): Report of a Case and Review of the Literature

September 7, 2005

Tailgut cysts are rare congenital lesions arising from remnants of normally regressing postanal primitive gut. They often present in middle-aged women with perirectal symptoms and a retrorectal multicystic mass. These cysts have occasionally shown malignant transformation. We report a case of a tailgut cyst occurring in a 25- year-old African-American female. The differential diagnosis of a retrorectal mass is briefly explored, and the etiology, diagnostic strategy, and surgical approach for tailgut cysts is examined. We also report an extensive literature review to examine clinical characteristics and surgical data for 43 cases of tailgut cysts spanning 16 years.

TAILGUT CYSTS, also known as retrorectal cystic hamartomas, are rare congenital lesions thought to arise from the remnants of the embryonic postanal gut. They predominantly occur as retrorectal multicystic masses in women. According to the largest case series by Hjermstad and Helwig in 1988 (n = 53),1 nearly half of the cases are asymptomatic and are frequently found on routine physical exam. When present, reported complaints include chronic perirectal pain and symptoms secondary to mass effect. Tailgut cysts occur in the company of a broad spectrum of diagnostic possibilities in the retrorectal space and, due to its rarity, the diagnosis is often delayed. Without complete excision, recurrence and infection are likely to occur. There have been 17 reported cases of malignancy arising from a tailgut cyst since 1988, further reinforcing the need for complete excision. We report a case of tailgut cyst occurring in an African-American female and review the literature.

Case Report

A 25-year-old African-American female with a previous diagnosis of recurrent perirectal abscesses presented with a 6-month history of increasing rectal pain, occasional rectal bleeding, and constipation. Two prior episodes with similar symptoms had occurred in the past, and she was treated with transrectal incision and drainage (l&D) 2 and 3 years earlier. A biopsy from an outside hospital reported no evidence of malignancy, and colonoscopy had shown compression of the anterior rectum without mucosal changes.

Physical exam revealed a moderately tender extrinsic rectal mass. CT scan showed a 9 7 cm fluid-filled cystic mass posterior to the rectum. At our institution, transrectal I&D was performed twice but failed to prevent the return of the mass and symptoms within months. Pathology from biopsy during these procedures only showed moderately inflamed dense fibrous tissue. MRI was performed (Fig. 1) and revealed a 6 7 cm trilobulated retrorectal mass displacing the rectum anteriorly. At this point, a developmental cyst was suspected, and complete surgical excision of the recurrent mass using a transsacral approach (Kraske method) was attempted.

Intraoperatively, three cystic compartments were identified with adhesions to pelvic floor musculature. Blunt and sharp dissection was used to separate the mass from the pelvic floor. The posterior lobule was entered and produced large amounts of opaque, gray fluid. The two lateral compartments were densely adhered to the fascia of the posterior rectum, and a small portion was left behind. The internal lining of the remaining portion was cauterized. Pathology from tissue obtained was consistent with a tailgut cyst and demonstrated multiple cysts lined by squamous columnar and transitional epithelium (Fig. 2). These were surrounded by dense fibrous tissue and poorly formed smooth muscle. Acute and chronic inflammation was noted, and there was no evidence of dysplasia.

The postoperative course was uneventful, and 6 months later there was no recurrence of the mass on CT (Fig. 3). One year later, the patient was without symptoms.

Discussion

The retrorectal space is a potential space developed when a mass displaces the rectum anteriorly. It is formed posteriorly by the sacrum and coccyx and anteriorly by the rectum. The pelvic peritoneal reflection forms the superior border, and the levator ani and coccygeus muscles form the inferior border. The lateral boundaries consist of the ureters and iliac vessels. 1-4

FIG. 1. Initial MRI demonstrating a well-defined multicystic mass in the retrorectal space.

The differential diagnosis of masses within this space is broad and includes primary tumors of neurogenic, osteogenic, and congenital origin, in addition to metastatic and inflammatory processes. Congenital lesions include chordomas (remnants of notochord), teratomas, anterior sacral meningoceles, and developmental cysts (dermoid, epidermoid, enteric duplication, and tailgut cysts).2, 3 Excluding inflammatory lesions, developmental cysts are the most common masses in the retrorectal space.2

Developmental cysts are distinguished by their histopathologic differences. Dermoid and epidermoid cysts are both lined with stratified squamous epithelium; however, only dermoid cysts contain dermal appendages (hair follicles, sweat glands, tooth buds). Dermoid cysts arise from faulty inclusion of ectoderm when the embryo coalesces. Epidermoid cysts are formed from inclusion of epidermal elements at the time of neural groove closure in the meninges. Rectal duplication cysts are lined by typical gastrointestinal epithelium (often with crypts, villi, and glands) and are surrounded by two well-formed layers of smooth muscle with nerve plexuses. There are several theories that speculate on their origin: persistence of fetal gut diverticula, defective recanalization of primitive gut, or a form of caudal twinning.1, 3, 5-8

Tailgut cysts (TGCs), or retrorectal cystic hamartomas, are predominantly multicystic and can contain a variety of epithelia between cysts or even within the same cyst. Epithelial types include stratified squamous, transitional, mucinous or ciliated columnar, and cuboidal mucus secreting. In contrast to enteric duplication cysts, TGCs have disorganized smooth muscle fibers within the cyst wall and do not contain neural plexuses.1-8

FIG. 2. Intraoperative photo showing trilobulated cystic structure.

FIG. 3. Medium power (100). On the left, keratin “pearls” are seen, suggesting squamous differentiation. Several cells on the right side of the field appear to contain intracellular mucin, suggesting glandular differentiation.

Defective embryological development of the hindgut region is thought to give rise to TGCs. During development, the embryo possesses a true tail containing the continuation of the primitive gut. The anus forms cephalad to the tail via invagination of the ectoderm (thus giving rise to the term “tailgut” or “postanal gut”). The remaining postanal gut is a tubular structure lined by two to four layers of stratified cuboidal epithelium. This eventually fills with epithelial debris and atrophies as the tail region regresses during the eighth week of development. The remnants of the primitive gut that fail to regress are believed to form TGCs. Origin from the neuroenteric canal has also been suggested.1, 3, 8

Middeldorpf described the first congenital cyst in the literature when he reported a presacral mass in a 1-year-old girl in 1885. In his report, he implicates a source from the tailgut but apparently describes a rectal duplication cyst. Nevertheless, many subsequent early authors referred to any presacral congenital cystic mass, most commonly teratomas, as Middeldorpf tumors.1, 3, 6, 8 Later, Peyron studied the embryonic tailgut, and in 1928 he concluded anterior sacrococygeal or retrorectal cystic masses to be of tailgut origin if their lining consisted of an intestinal-type epithelium and they lacked a definite muscular or serous coat.1, 6 In their report in 1988, Hjermstad and Helwig reinforced the stipulation of absence of a well-defined muscular wall with myenteric plexuses to exclude duplication cysts.1 Numerous terms have been used in the literature to describe these tailgut remnants, including “tailgut vestige,”"postanal gut cyst,”"retrorectal cystic hamartoma,” and “tailgut cyst.”

TABLE 1. Clinical Data

Hjermstad and Helwig reported the largest case series of tailgut cysts (n = 53) and described the clinical characteristics. They found TGCs presented at any age but did so predominantly in middle- age, appearing as multicystic masses in the retrorectal space. They also found a 3:1 female to male ratio. Approximately half of the patients were symptomatic, with the most common symptoms being perirectal pain and symptoms of mass effect: rectal fullness, constipation, painless rectal bleeding, change in caliber of stool or urinary frequency. In asymptomatic patients, TGCs were found on routine rectal or pelvic exam. Signs associated with TGC include draining sinuses and a funnel-shaped postanal dimple. They reported that malignancy arising from a TGC was rare with a few cases of widespread metastases and death.1

The differential diagnosis for a retrorectal mass can be narrowed using a combination of diagnostic tools to reach a preoperative diagnosis of a developmental cyst. Due to their location, almost all retrorectal tumors will be palpable on rectal examination, and developmental cysts will manifest as extrinsic masses.2, 3 Colonoscopy could rule out any rectal mucosal changes in cases of rectal bleeding. Bari\um enema can only further characterize lesions as extrinsic to the rectum and provides no additional information.2, 3 Endorectal ultrasound has been used to characterize the lesion as cystic and occasionally shows internal echoes due to mucoid or inflammatory debris.1, 3, 5, 9, 10 Radiographie workup has included plain films to rule out bone destruction indicative of metastases or osseous lesions. The main CT findings for developmental cysts are of a well-defined thin-walled cystic retrorectal mass often with compression of the posterior rectum (without invasion of rectal wall). Further, CT can identify bony destruction or calcifications indicating malignancy or solid portions of a teratoma. Rarely, thin calcifications have been reported on CT of tailgut and dermoid cysts.5, 11-13 There are limited reports of MR findings of TGCs, but they describe a retrorectal mass with hypointense T!-weighted images and hyperintense T2-weighted images. MRI has limited ability to detect calcifications but can diagnose fatty tumors using fat suppression, and sagittal films can evaluate structural relationships.11, 14, 15 The differentiation between a retrorectal component of a perineal abscess is difficult. Recurring abscesses in the retrorectal space, repeated operations for an anal fistula, or inability to locate infection sites for anal, perianal, or rectal sinus should raise suspicion for a retrorectal cyst.2, 3, 5, 14, 15

The definitive diagnosis and treatment of a TGC is through complete surgical excision. Biopsy should not be attempted (unless the mass is surgically unresectable at presentation) due to risk of spreading dysplastic cells through weakened cyst walls. In addition, tissue obtained from biopsy is often not extensive enough to show all the histologie features necessary for diagnosis.1, 3, 6, 16 Complete excision is necessary to prevent recurrence, infection, and possible malignant transformation. For most lesions, a posterior approach with removal of a portion of the coccyx will allow the best visualization and removal of the multiloculated cysts.1-3, 8 In the 188Os, a German surgeon named Kraske first described an approach to the retrorectal space. The Kraske method uses a longitudinal incision, but other posterior transsacral approaches use a transverse incision over the sacrococcygeal joint.8 In the posterior approach, the patient is in the prone jackknife position, a portion of the coccyx is removed, and a plane is defined between the posterior rectal wall and the mass.3, 4 Cysts dissected from the rectal wall benefit from a finger in the rectum for tactile feedback. Surgical scars and tracts from previous incisions and drainage should be completely excised. In the case of larger tumors, those above the sacral promontory, or when malignancy is suspected, a combined abdominal-sacral approach may be used. The retrorectal space is first approached through the abdomen, where the rectosigmoid colon is mobilized and control of the iliac vessels is accomplished. Then, a similar transsacral approach can be tried but with the benefit of vascular control and identification of structures from above.3, 4, 8

Since Hjermstad and Helwig published their findings in 1988, there have been no large case series reported. From our review of the literature (keyword = tailgut cyst or retrorectal cystic hamartoma, limits = English), there have been 43 cases with confirmed diagnosis of TGC since their report. All cases with a conclusive pathological diagnosis of tailgut cyst were included, as well as those that occurred outside the retrorectal space. Many of the previously known clinical aspects of TGCs were reinforced (Table 1). The female to male ratio was approximately 3 to 1 (33 to 10). Excluding three neonates, women and men had an average age of 43.8 and 50.1 years at presentation (t test, P = 0.43), respectively. Review of the literature revealed only one other verified case of a tailgut cyst occurring in an African-American adult. However, most studies do not clarify race, so this significance is not entirely clear. Clinical presenting signs and symptoms were also similar to previous reports, and we found 39 cases where this information was known. Twenty patients (51.3%) presented with complaints of perirectal symptoms from mass effect: pain, decreased stool caliber, constipation, fullness, rectal bleed. Seven (17.9%) complained of abdominal, pelvic, or flank pain; however, only four of these had TGCs in the retrorectal space. Six (15.4%) presented with anorectal signs (recurrent fissures, fistulas, pilonidal abscess, anal stenosis, sacral dimple). Three (7.7%) presented only with enlarging sacrococcygeal soft tissue masses: two of these patients were neonates. Earlier reports indicate that almost 50 per cent of TGCs were found on routine pelvic or rectal examinations. Interestingly, only four (10.3%) patients were asymptomatic and had their masses found on routine exams. Note that the sum of the numerators is 40 because one patient presented with both perianal pain and a recurrent anal fistula.

TABLE 2. Surgical and Follow-up Data

TGCs almost exclusively occur within the retrorectal space; however, our review showed 16.3 per cent (7/43) of the confirmed cases occurred outside the retrorectal space: two perirenal,21, 24 two subcutaneous in anorectal region.16, 20 two subcutaneous sacrococcygeal,22, 30 and one anterior to the rectum.19 The perirenal location has been theorized to be due to unregressed tailgut involvement in the path of ascending kidney development.21, 24 Seventeen cases of malignancy arising from within a TGC were found: 11 adenocarcinomas,6, 7, 11, 14,,19, 25, 25, 31, 34 5 carcinoids,20, 17, 23, 32, 37 and 1 neuroendocrine.6 There is some debate in the literature about the classification of one case of carcinoid versus neuroendocrine,23 but it has been classified as carcinoid here.

Surgical data (Table 2) from these cases were reported irregularly, but we were able to find 38 excisions of TGCs (including two recurrences) within the retrorectal space. However, only 28 cases described specific procedures. The posterior approach was used most frequently (46.4%, 13/28), and five of these were associated with malignancy. Only seven cases using the posterior approach for TGCs in the retrorectal space provided follow-up data.10, 19, 26, 29, 31, 34, 36 There were no recurrences, and disease-free survival was reported at 0.5, 12, 12, 18, 38, and 60 months and 1-5 years. A variety of other surgical approaches were used as shown in Table 2.

Seven recurrences were reported, and five of these had a known initial procedure. Three cases of TGCs with malignant degeneration had recurrence of disease. Twelve months after abdominoperineal resection of a 2-cm submucosal anorectal TGC associated with carcinoid, liver and brain metastases were discovered.20 An adenocarcinoma within a 16-cm TGC in the retrorectal space recurred with metastases at 6 months (death occurred at 14 months) after a combined abdominosacral approach.28 A 13-cm TGC with adenocarcinoma recurred at 4 years after a radial approach.7 Two cases reported recurrences of TGCs without associated malignancy after excision of the tumor within the retrorectal space: 2 years after laparotomy and 1 year after transanal excision.3, 29 There is evidence of increased morbidity associated with improper treatment, with at least four cases of multiple I&Ds that failed to prevent the return of symptoms.26, 29, 34

Tailgut cysts are rare lesions but are being reported with increasing frequency in the literature. There is a case report of a tailgut cyst causing pelvic outlet obstruction as well as being associated with a pilonidal sinus.39, 40 They present predominantly in middleaged females with perirectal symptoms as a multicystic mass located in the retrorectal space. The diagnosis is often delayed and can be difficult to distinguish from an inflammatory process. Arrival at a clinical diagnosis of developmental cyst can be achieved through a combination of history and physical exam, colonoscopy, and CT/MRI imaging. Biopsy should be avoided if possible. Complete surgical excision using a transsacral or an abdominosacral approach is necessary for diagnosis and definitive treatment. Index of suspicion should be high for women with a multicystic retrorectal mass, especially if not responding to previous attempts at incision and drainage.

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CHRISTOPHER KILLINGSWORTH, M.D., THOMAS R. GADACZ, M.D.

From the Department of Surgery, Medical College of Georgia, Augusta, Georgia

Presented at the Annual Scientific Meeting and Postgraduate Course Program, Southeastern Surgical Congress, New Orleans, LA, February 11-15, 2005.

Address correspondence and reprint requests to Thomas R. Gadacz, M.D., Department of Surgery, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912.

Copyright The Southeastern Surgical Congress Aug 2005




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