Anus & perianal
Benign / nonneoplastic lesions
Tailgut cyst

Topic Completed: 1 November 2014

Minor changes: 20 August 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Tailgut cyst [title]

Elliot Weisenberg, M.D.
Page views in 2019: 4,145
Page views in 2020 to date: 1,131
Cite this page: Weisenberg E. Tailgut cyst. website. Accessed May 24th, 2020.
Definition / general
  • Cystic presacrococcygeal anal canal mass lesion believed to arise from tailgut embryonic remnants (note: in embryogenesis, humans have a true tail that is greatest in size at 35 days of gestation that then regresses)
  • Also called retrorectal cystic hamartoma
  • Very rare, more common in women
  • Presacrococcygeal anal canal
  • Believed to arise from tailgut (postanal gut)
Clinical features
  • Lesions usually become apparent during adulthood due to pain, discomfort, rectal bleeding, infection or malignant transformation (neuroendocrine tumor, adenocarcinoma, urothelial carcinoma, Arch Pathol Lab Med 2000;124:725)
  • May be an incidental finding
  • Imaging studies may suggest diagnosis but surgical specimen is necessary for diagnosis
  • Extensive sampling is recommended to exclude malignancy
  • Rarely diagnosed by fine needle aspiration (Acta Cytol 2014;58:217)
Radiology description
  • Multiloculated presacrococcygeal mass
Prognostic factors
  • When benign, excision is curative
Case reports
  • Complete surgical excision
Gross description
  • 2 - 12 cm (mean 9.5 cm) multilocular cyst
Microscopic (histologic) description
  • Multilocular cyst with squamous, mucinous, simple, pseudostratifed ciliated or transitional lining
  • May contain bundles of smooth muscle in cyst wall
  • Meningeal tissue, thyroid tissue and glomus bodies have also been reported
Microscopic (histologic) images

Images hosted on other servers:

Cyst lining

With adenocarcinoma

With carcinoid

Differential diagnosis
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