Tailgut cyst, management of a rare perianal mass: a case report

Introduction

A perianal mass may indicate a variety of illnesses, including hemorrhoidal thrombosis, abscess, tailgut cyst, dermoid or epidermoid cyst, teratoma, rectal prolapse, or anal lipoma (1,2).

Among these diagnoses, tailgut cyst is an intestinal cyst of embryonic origin which can remain undetected for years. This rare disorder usually manifests itself in the retro-rectal area. According to the Mayo Clinic’s 19-year experience, the incidence of retro-rectal mass hospitalization is 1/40,000 (3).

It is rarely located at the anal level only, without extending behind the rectum. The hamartoma’s enormous cellular production requires the exclusion of any potential malignant change (4). If left untreated, it might cause perianal sepsis. We present this case in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-24-133/rc).

Case presentation

A 59-year-old male sought medical attention for a painless but bulging and uncomfortable perianal tumour. A clinical examination in a lithotomy position revealed a 3 cm diameter soft mass on the posterior anal margin. On palpation, a haemorrhoidal disease was excluded. The patient denied any history of surgery, or family history of colorectal cancer, the patient had thrombophlebitis, and he was a smoker.

A pelvic nuclear magnetic resonance revealed a large ovoid lesion originated from the posterior wall of the anal canal, located between the external sphincters and prolapsed into the intergluteal area. The liquid content showed no sign of tissue contrast enhancement. The radiologist did not describe any apparent sign of malignancy but was unaware of the precise nature of the mass (Figures 1,2).

Figure 1 Pelvic nuclear magnetic resonance, series of transverse sections. The arrow indicates the location of the tailgut cyst behind the anal canal protruding outside.

Figure 2 Pelvic nuclear magnetic resonance, frontal section, profile view of the hamartoma located with the arrow.

The surgeon removed the mass under general anaesthesia. To perform the surgery, the patient was placed in a lithotomy position. The mass (Figure 3) was dissected using a bipolar scalpel, by performing a circumferential incision of the skin and the subcutaneous tissues. The surgery was conducted in the aim of limiting any potential damage to the sphincter. Under macroscopic examination, no further trace of the cyst could be detected after the operation. The surgery has lasted 15 minutes without any complications and the pathologist received the surgical specimen.

Figure 3 Macroscopic view of the protuberant anal lesion before intraoperative resection.

Microscopic examination confirmed a perianal cyst (Figure 4A-4D). It revealed a squamous epithelium-lined anal mucosa with no atypia. The cystic lesion was surrounded by both a squamous epithelium and a pseudostratified ciliated epithelium made up of goblet cells or mucus cells. The polynuclear neutrophils infiltrated the epithelium, which are occasionally abraded and replaced by macrophages, generating a pseudo-palisade. There were no signs of malignity. The margin is healthy but less than one millimeter apart (Figure 4D); nevertheless, the cyst was completely removed. Therefore, no additional treatment has been necessary, and there was a favourable prognosis.

Figure 4 Pathological sections of the tailgut cyst in hematoxylin and eosin staining with a zoom of 5 mm on the cyst (A), 100 µm with the arrow indicating the ciliated epithelium containing goblet cells (B), 250 µm on the squamous and ciliated epithelium indicated by the arrows (C), and 5 mm on the entire section of the cyst surrounded by the green line and entirely removed with the healthy margin less than 1 mm apart represented by the blue line (D).

The patient’s clinical outcome was uneventful two weeks following surgery. He did not complain of incontinence, and he was satisfied with the treatment. Although a consultation was planned six months after the surgery, the patient decided to interrupt a follow-up he considered unnecessary.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

An exclusive localization on the anal canal is quite unusual. Only five cases describing such a localization for this pathology can be identified in the existing literature since 2016, including three males and two women (1,2,4-6). Except for a 20-year-old woman mentioned by Arshad et al. (2), the age ranging was from 50 to 72 years for four cases (1,4-6). Based on the existing tailgut cysts series, female gender is the majority (3,7,8). They are rarely identified and removed in newborns or children (9-11).

The remaining cases are often localized in retro-rectal area, with some of them reaching the anal canal (12). The other rare localizations are intradural (13), prerectal or perirenal.

The few exclusively anal cases existing and the only case described in this article is the main limitation of the study, because it is responsible for the impossibility of generalizing. Moreover, the patient’s incompliance prevents us from carrying out long-term follow-up. However, the strength of the article is that it allows rare cases to be brought to light.

Tailgut cysts are rarely painful when perianal. Often, patients consult for cosmetic reasons or to alleviate anal discomfort.

In general, the macroscopic aspect is polypoid with skin coverage, the axis ranging between 5 and 6.5 cm for perianal cases (2,4,6). Due to its appearance and rarity, it is frequently confused with a pelvic abscess (5). In our case, the gastroenterologist first thought that it could be a hypertrophied skin tag, presenting an atypical aspect.

Sun and colleagues (7) proposed that injected tomography could be an adequate preoperative assessment. Others authors did a nuclear magnetic resonance with an experienced radiologist because it is non-invasive and helpful in recommending a diagnosis (14). In our case, the medical team requires a nuclear magnetic resonance that helps to describe the mass, but the radiologist was not able to give a diagnosis. Therefore, the confirmation of the diagnosis requires a resection and a pathological investigation.

In benign cases like ours and in this localization, we consider that postoperative clinical follow-up with an anoscopy is enough, considering that it allows an easy access to the initial lesion. The malignant transformation is rare and only few cases are described (6), and it would represent between two and thirteen percent of tailgut cyst according to Haval et al. (15). There is a single article presenting a high malignant transformation rate of twenty-six percent (10), but this result is controversial (16,17). In malignant cases, an adjuvant treatment with chemotherapy or radiotherapy is necessary (6). The literature describes several forms of possible tumours, including neuroendocrine tumour (12), adenocarcinoma (5), and transitional cell carcinoma (18).

During resection, other authors described a creamy brownish or yellowish liquid (1,2,4) but in our case, the cyst has not been opened before being sent to the pathologist, because of a risk of potential dissemination (19). For the resection of retro-rectal cases, different techniques exist including: the low retro-rectal route, trans-anal endoscopic, laparoscopic trans-abdominal, or posterior trans-sacral. A review of the literature on tailgut cysts confirmed the need of a complete resection (14), given the risks of recurrence or infection with a partial resection.

In our case, the perianal and protuberant localization, the atypical and non-inflammatory aspect, and the uncertainty of the nuclear magnetic resonance allowed the indication of a complete resection. We choose to do the resection using a trans-anal route with the patient in a lithotomy position, because the cyst was in the same position as a hemorrhoid, and this allowed a good view. This position was judged most suitable to remove the cyst, while limiting the traumatic risks for the tissues. We were confident about the function of the anal sphincter, even though a small part of this sphincter might have been affected. The benignity of the lesion consolidated the chosen approach and avoided adjuvant treatment.

Pathological investigation for tailgut cysts reveals always several forms of squamous and stratified epithelia as in our case. Our pathologist also confirmed that the margins were healthy (less than one millimeter). Given the absence of malignancy and the risk to the patient’s physical integrity, we considered that an infracentimeter margin was sufficient.

Knowing that a recurrence is always a possibility (20), even if there are very few described (6), and given healthy margins of less than one millimeter, we initially planned to follow the patient clinically every six months. In case of clinical doubts, we would perform a nuclear magnetic resonance but not a biopsy because of the risk of dissemination.

Conclusions

Perianal tailgut cyst is a rare diagnosis that should be considered when identifying perianal tumours. Nuclear magnetic resonance can suspect the diagnosis and describe these masses but could remain insufficient, especially for inexperienced radiologist. Pathology confirms the diagnosis. In the absence of malignancy, full surgical resection with a trans-anal route and a clinical follow-up are adequate.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-24-133/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-24-133/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-24-133/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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