Perianal Tailgut Cyst: An Unusual Presentation

Abstract

A tailgut cyst (TGC) is a rare congenital lesion that occurs due to failure of involution of the distal hindgut, leading to the development of a mucus-secreting cyst. The clinical presentation is nonspecific, and often the diagnosis can be missed. We present the case of a 20-year-old female with a TGC in the perianal region. Surgical excision of the cyst was performed, followed by an uneventful recovery. The young age of our patient and the anatomical location of the TGC make our case a rare entity, highlighting the need for practicing surgeons to keep TGC as a differential in mind while examining masses in the perianal region.

Keywords: pedunculated mass; perianal cyst; perianal lesion; surgical case reports; tailgut cyst.

Figure 1. Tailgut cyst.

Images 1A and 1B show the patient in lithotomy position with the tailgut cyst protruding out of the anal canal. It had a soft consistency and a smooth surface covered with skin.

Figure 2. Axial MRI scan of the tailgut cyst.

This MRI scan shows a hyperintense lobulated soft tissue lesion (red arrow) in the region of the anal canal (white arrow). It arises from the external anal sphincter on the left side at the 4 o'clock position. It bulges into the anal canal and laterally has a mild mass effect on the left ischiorectal fossa (yellow arrow). Also shown for reference is the sigmoid colon (blue arrow).

Figure 3. Surgical excision of the tailgut cyst.

The figure shows the cyst being dissected out from the surrounding tissues, still attached to the anal verge at its pedicle.

Figure 4. Histopathological sections of the excised specimen.

The specimen is lined by stratified squamous epithelium (black arrows) with areas of transitional and pseudostratified ciliated columnar epithelium in between. Both Figures 4A (right) and 4B (left) demonstrate cystic spaces (*) surrounded by fibromuscular stroma (F). Interspersed between the stroma, a variety of lymphocytes can be seen (L).