Anus & perianal area

Other nonneoplastic

Tailgut cyst



Last author update: 31 July 2023
Last staff update: 31 July 2023

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PubMed Search: Tailgut cyst

John D. Paulsen, M.D.
Alexandros D. Polydorides, M.D., Ph.D.
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Cite this page: Paulsen JD, Polydorides AD. Tailgut cyst. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anustailgutcyst.html. Accessed March 28th, 2024.
Definition / general
  • Cystic developmental anomaly of the retrorectal / presacral space that is thought to arise from remnants of the embryonic tailgut
Essential features
  • Congenital, well demarcated, usually multiloculated, cystic lesion of the retrorectal / presacral space that is thought to arise from remnants of the embryonic tailgut
  • Preoperative diagnosis relies on imaging, as fine needle biopsy is not recommended due to risk of infection or seeding of tumor cells
  • Multiple types of epithelial linings have been described; stratified squamous epithelium is most common (~75%)
  • Cyst wall shows disorganized / irregular smooth muscle bundles without neural plexi
  • Prognosis depends upon presence or absence of malignant transformation, which can be seen in up to ~25% of cases (usually as either adenocarcinoma or well differentiated neuroendocrine tumor)
Terminology
ICD coding
  • ICD-10: K62.89 - other specified diseases of anus and rectum
Epidemiology
Sites
  • Retrorectal / presacral space
  • Retrorectal / presacral space is a potential space defined by the following boundaries (AJR Am J Roentgenol 2017;209:790)
    • Anterior: rectum
    • Superior: pelvic peritoneal reflection
    • Inferior: levator ani muscles
    • Posterior: presacral fascia, sacrum and coccyx
    • Lateral: iliac vessels and ureters
Pathophysiology
  • Considered a developmental anomaly
  • Precise embryological origin is uncertain but likely is a remnant of the distal hindgut that extends into the vestigial / embryonic tail (Histopathology 2023;82:232)
  • Involution of the embryonic tailgut occurs by the eighth week of gestation; failure of regression is thought to give rise to tailgut cyst (Arch Pathol Lab Med 2000;124:725)
Diagrams / tables

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Retrorectal space

Retrorectal space

Clinical features
  • Clinical presentation
    • ~50% asymptomatic
    • Symptoms are usually nonspecific and due to local mass effect
      • Constipation, decreased stool caliber, rectal pain, rectal fullness, obstruction, tenesmus, rectal bleeding (usually painless), discomfort while sitting, dysuria, urinary retention, lower limb neurological symptoms due to sacral plexus compression (Ann Coloproctol 2019;35:268)
    • Rarely presents as prolapsing cyst through the anus (Eur J Pediatr Surg 2013;23:e3)
  • Physical exam findings
  • Secondary infection may lead to sepsis or abscess formation
Diagnosis
  • Pelvic magnetic resonance imaging (MRI)
  • Ultrasound guided needle biopsy is not recommended due to risk of infection or seeding of tumor cells (Int J Colorectal Dis 2007;22:1283)
Radiology description
  • Ultrasound
    • Cystic lesion with internal echoes from inflammatory debris or mucus
  • Computed tomography (CT)
    • Well defined cystic mass in retrorectal space
    • Water or soft tissue density
    • Loss of well defined margins and bone destruction may be seen with malignant transformation
  • Pelvic MRI (Ann Coloproctol 2019;35:268)
    • Well defined cystic mass in retrorectal space
      • Hypointense T1 weighted
      • Hyperintense on T2 weighted
    • Loss of well defined margins and bone destruction may be seen with malignant transformation
Radiology images

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Tailgut cyst, malignant transformation

Retrorectal cystic mass

Tailgut cyst, malignant transformation

Malignant transformation

Prognostic factors
  • Prognosis depends upon presence or absence of malignant transformation
  • Excision is curative in cases without malignant transformation
  • Overall metastatic potential of cases with malignant transformation is unclear, although distant metastasis has been reported (Medicine (Baltimore) 2020;99:e20941, Clin Case Rep 2023;11:e6893)
Case reports
Treatment
  • Complete surgical resection with adequate margins
    • Confirmation of diagnosis
    • Symptom relief
    • Prevention of malignant transformation
  • Surgical approach may be anterior (transabdominal with laparoscopy), posterior (paracoccygeal) or combined, depending on tumor size and position (Ann Coloproctol 2019;35:268)
  • Adjuvant chemotherapy and radiotherapy in cases with carcinoma transformation
Clinical images

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Posterior approach view of tailgut cyst, intraoperative photograph

Posterior approach view

Gross description
Gross images

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Tailgut cyst, intact resection

Intact resection

Tailgut cyst, mud-like contents

Mud-like contents

Tailgut cyst adenocarcinoma

Tailgut cyst adenocarcinoma

Microscopic (histologic) description
  • Multiple types of cyst lining have been described
    • Stratified squamous epithelium (most common, ~75%), likely representing a metaplastic response to inflammation (Am J Clin Pathol 1988;89:139)
      • Keratinizing or nonkeratinizing
    • Columnar epithelium
      • Pseudostratified, stratified, goblet cell containing, ciliated
    • Transitional epithelium
    • Mucinous epithelium
    • Cuboidal epithelium
  • More than 1 type of epithelial lining may be seen within a single cyst
  • Surrounding dense fibroconnective tissue stroma with disorganized / irregular smooth muscle bundles that lack neural plexi
  • Histologic evidence of rupture may be seen
    • Acute and chronic inflammation
    • Xanthogranulomatous reaction
  • Neoplastic transformation in ~25% of cases as per comprehensive 2019 meta analysis (Colorectal Dis 2019;21:869)
Microscopic (histologic) images

Contributed by John D. Paulsen, M.D. and Alexandros D. Polydorides, M.D., Ph.D.
Dense fibroconnective tissue stroma

Dense fibroconnective tissue stroma

Disorganized smooth muscle

Disorganized smooth muscle

Epithelial linings

Epithelial linings

Multiple loculations

Multiple loculations

Mucinous columnar epithelium

Mucinous columnar epithelium

Neoplastic transformation, neuroendocrine tumor

Neoplastic transformation, neuroendocrine tumor

Sample pathology report
  • Retrorectal space, excision:
    • Tailgut cyst (see comment)
    • Comment: Sections show a benign cyst lined by stratified squamous, transitional and ciliated columnar epithelium. Disorganized bundles of smooth muscle are present in the cyst wall, without neural plexi. The findings are consistent with a diagnosis of tailgut cyst (synonym: retrorectal cystic hamartoma). There is focal epithelial disruption with associated xanthogranulomatous inflammation, suggestive of rupture.
Differential diagnosis
  • Rectal duplication cyst:
    • Lined by rectal mucosa with crypts
      • May show heterotopic elements (e.g., gastric, bronchial)
    • Cyst lumen contains mucin
    • Well developed smooth muscle layer resembling muscularis propria (2 layers, often with nerve plexi)
    • Shows continuity with rectum, grossly or microscopically
    • Usually unilocular
  • Epidermoid cyst:
    • Lined by keratinizing squamous epithelium
    • Cyst lumen contains keratinous debris
    • No associated smooth muscle or adnexal structures within cyst wall
    • Usually unilocular
  • Dermoid cyst:
    • Lined by keratinizing squamous epithelium
    • Cyst wall shows associated skin adnexal structures (hair follicles, sebaceous glands, sweat glands)
    • Cyst lumen contains keratinous debris and oily material
    • No associated smooth muscle within cyst wall
    • Usually unilocular
  • Neurenteric cyst:
    • Lined by columnar or cuboidal cells with or without cilia
    • Diagnosis is established by presence of glial tissue or connection to spinal cord
  • Anterior sacral meningocele:
    • Lined by attenuated arachnoid cells
    • Communicates with subarachnoid space
    • Usually unilocular
    • Radiographic scimitar sign is pathognomonic (Dis Colon Rectum 1988;31:806)
  • Anal gland cyst:
    • Communicates with anal duct or crypt
    • Located near anal sphincter
    • Cyst lumen contains mucin
  • Sacrococcygeal teratoma:
    • Contains derivatives of 2 or more germ layers (ectoderm, mesoderm, endoderm)
    • Mature tissue elements, immature tissue elements or both may be seen
    • Usually solid but cystic areas may develop (Dis Colon Rectum 1988;31:806)
    • Most present in infancy or childhood
  • Sacrococcygeal chordoma:
    • Usually an expansile intraosseous mass, rather than cystic
    • Epithelioid cells with clear to eosinophilic cytoplasm and vacuoles (physaliphorous cells)
    • Extracellular myxoid matrix
    • Positive for S100 and brachyury by immunohistochemistry
Board review style question #1

A 54 year old woman presented with rectal fullness and was found to have a cystic tumor in the retrorectal space on pelvic magnetic resonance imaging (MRI). The lesion was surgically resected and is shown above. Which of the following, if found on histologic examination, would be most suggestive of a tailgut cyst?

  1. Cyst lining comprised of attenuated arachnoid cells
  2. Cyst lining of rectal mucosa with associated well developed smooth muscle layer within the cyst wall
  3. Fibroconnective tissue containing disorganized smooth muscle bundles within the cyst wall
  4. Keratinizing stratified squamous epithelial lining with associated skin adnexal structures
  5. Physaliphorous cells showing immunoreactivity for brachyury
Board review style answer #1
C. Fibroconnective tissue cyst wall containing disorganized smooth muscle bundles is characteristic of tailgut cysts. Answer B is incorrect because an associated well developed smooth muscle layer that is muscularis propria-like and often with nerve plexi is seen in rectal duplication cysts. Answer A is incorrect because a cyst lining comprised of attenuated arachnoid cells is featured in anterior sacral meningoceles. Answer D is incorrect because keratinizing stratified squamous epithelial lining with associated skin adnexal structures is seen in dermoid cysts. Answer E is incorrect because physaliphorous cells showing immunoreactivity for brachyury is found in cystic sacrococcygeal chordomas.

Comment Here

Reference: Tailgut cyst
Board review style question #2
A 59 year old woman presented with constipation and was found to have a cystic tumor in the presacral space. The lesion was surgically resected and submitted for histopathological evaluation. A diagnosis of tailgut cyst was rendered. Which of the following is true regarding the diagnosis?

  1. Fine needle biopsy is recommended prior to surgical excision
  2. Prognosis depends upon the presence or absence of malignant transformation
  3. Squamous cell carcinoma is invariably present on microscopic examination when the lesion is completely submitted for histopathological evaluation
  4. Tends to be unilocular
  5. The cyst wall usually contains a well developed smooth muscle layer with nerve plexi
Board review style answer #2
B. The prognosis of tailgut cysts depends upon the presence or absence of malignant transformation. It is reported that up to ~25% of tailgut cysts show malignant transformation, most commonly as adenocarcinoma or well differentiated neuroendocrine tumors, although squamous cell carcinoma, adenosquamous carcinoma, transitional cell carcinoma and sarcoma have also been reported. Answer A is incorrect because fine needle biopsy is not recommended prior to surgical excision due to risk of infection or seeding of tumor cells. Answer C is incorrect because squamous cell carcinoma arising in association with tailgut cyst is extremely rare and limited to case reports. Answer D is incorrect because tailgut cysts are typically multilocular (~80%). Answer E is incorrect because tailgut cysts show disorganized / irregular smooth muscle bundles without nerve plexi within the cyst wall, as opposed to rectal duplication cysts, which show a well developed smooth muscle layer (muscularis propria-like) with nerve plexi.

Comment Here

Reference: Tailgut cyst
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