A 26 year old woman with a history of perineal pain and anal discharge underwent a pelvic MRI because of a suspicion of an anorectal abcess. On the MRI, there was a 3cm heterogeneous lesion with an elevated protein content, located in the retro-rectal space. Because the differencial diagnosis was between dermoid/epidermoid cyst and endometriosis, an endoscopic ultrasound was preformed. This exame revelead a 3cm heterogeneous lesion with some cystic areas, causing compression of the rectal wall (Image 1).

Image 1 – Endoscopic ultrasound: 3cm heterogeneous lesion with some cystic areas,

causing compression of the rectal wall


Fine-needle-aspiration with a 22-gauge needle, single pass was performed. The cytological examination revealed frequent cylindric cells without atypia, most of them with terminal bar, some with cillia cystic, with no evidence of malignancy compatible with tail-gut cyst (image 2). The patient underwent a laparoscopic resection, which confirmed a tailgut cyst.

Image 2 – Fine needle aspiration smears: frequent cylindric cells without atypia,

most of them with terminal bar, some with cillia (HE, x400)


Retro-rectal cystic hamartoma, also known as tailgut cyst, is rare congenital developmental lesion arising from post-natal primitive gut remnants, generally located in the retro-rectal space(1). Usually found in asymptomatic middle-aged women, complications can occur due to the local mass effect on surrounding organs (rectal fullness, constipation, painful defecation), infection (cysts with secondary infection have typical symptoms of anorectal or pelvic abscess and fistula, or peri-anal sinus), bleeding or malignant transformation(2). Endoscopic ultrasonography (EUS) shows multilocular cystic lesions with internal echoes due to mucoid material or inflammatory debris(3). The common cytologic features of the specimens are ciliated epithelial cells, proteinaceous material with degenerated debris, and benign appearing epithelium of squamous and/or gastrointestinal type that lack cytologic atypia. The identification of ciliated columnar cells is the key finding(4). Surgical excision is the gold-standard treatment. There are only few cases of tail gut cysts diagnosed by EUS fine neddle aspiration (FNA) with a flexible echoendoscope(3,4,5). Puncture by EUS-FNA is acurate and should be performed when other etiologies are considered or if malignant degeneration changes management(3).



1 Lim SW, Huh JW, Kim YJ, Kim HR: Laparoscopy-assisted resection of tailgut cysts: report of a case. Case Rep Gastroenterol 2011, 14:22–27.

2 Kildušis E, Samalavičius NE. Surgical management of a retro-rectal cystic hamartoma (tailgut cyst) using a trans-rectal approach: a case report and review of the literature. Journal of Medical Case Reports 2014, 8:11

3 Pinto-Marques P, Damião-Ferreira J, Mendonça E, et al. Unusual cause of CA 19.9 elevation diagnosed by endoscopic ultrasound-guided fine needle aspiration: a retrorectal tailgut cyst. Endoscopy. 2012;44 Suppl 2

4 Hall D, Pu R, Pang Y. Diagnosis of foregut and tailgut cysts by endosonographically guided fine-needle aspiration. Diagn Cytopathol 2007; 35: 43-46.

5 Siddiqui FA, Chopra R, Al-Marzooq Y. Fine needle aspiration cytology diagnosis of tailgut cyst: a rare entity. Acta Cytol. 2014;58(2):217-20. 2014:17.



Iolanda Cristina Teixeira Ribeiro(1), Sónia Alexandra Sousa Fernandes(1), Maria Luísa Proenca(1), Davide Tente(2)

1 – Hospital Center of Vila Nova Gaia, department of Gastroenterology and Hepatology;

2 – Hospital Center of Vila Nova Gaia, Department of Anatomic Pathology