Case Report

A carcinoid tumour arising within a tailgut cyst: a diagnostic challenge

Scottish Medical Journal 2014, Vol. 59(1) e14–e17 ! The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0036933013519029 scm.sagepub.com

JH Kim1, S-Y Jin2, SS Hong3 and TH Lee1

Abstract A 49-year-old man was referred with constipation that had lasted for a few months. On colonoscopy, a subepithelial tumour more than 4 cm in size was seen in the rectum. He underwent endoscopic ultrasound and pelvic magnetic resonance imaging. He was preoperatively diagnosed with a rectal duplication cyst based on imaging studies. However, the final histopathologic diagnosis after transanal excision of the rectal mass was rectal carcinoid tumour with tailgut cyst. Tailgut cysts are very rare congenital lesions in the presacral area and are most often discovered incidentally in middleaged women. It is difficult to distinguish the imaging appearance of tailgut cysts from that of many other retrorectal cysts. Malignant transformation of tailgut cysts has been estimated to occur in 2 to 13% of cases. We report the diagnostic difficulties encountered in a case of carcinoid tumour arising from a tailgut cyst in a male patient.

Keywords Rectum, carcinoid tumour, tailgut cyst, diagnosis

Introduction Tailgut cysts or retrorectal cyst hematomas are rare malformative cystic lesions that are found in the retrorectal space, usually in women, but have been reported in all age groups.1 They are embryologically considered to arise from persistent remnants of the postanal gut (tailgut).1 However, a variety of other cystic lesions, including rectal duplication cysts, cystic sacrococcygeal teratomas, epidermal cysts, epidermoid cysts, and anal duct or gland cysts, neuroenteric cysts, anterior sacral meningocele, necrotic rectal leiomyosarcoma, cystic lymphangioma and pyogenic abscess, occur in the retrorectal area. The distinction of a tailgut cyst from other retrorectal cysts is important because of the malignant potential of tailgut cysts.2 To the best of our knowledge, there have been only 17 reported cases of carcinoid tumour with tailgut cysts and only four reported cases in male patients.3 Diagnosis of a carcinoid tumour with tailgut cysts is difficult even using the most advanced imaging techniques, including endoscopic ultrasound (EUS) or magnetic resonance imaging (MRI). We report herein the diagnostic difficulties encountered in a case of carcinoid tumour arising from a tailgut cyst in a male patient.

Case report Medical history A 49-year-old man was admitted to our hospital because of constipation that had developed a few months before. The patient had no history of diabetes mellitus, hyperlipidemia or hypertension and did not take any medications.

Clinical features and investigations The patient’s vital sign was stable and in physical examination, a huge and soft mass was palpated at the posterior rectum on digital rectal examination. His hematological and biochemical blood testing were unremarkable as were tumour markers. The results of 1

Doctor of Medicine, Department of Internal Medicine, College of Medicine Soonchunhyang University Hospital, Seoul, Korea 2 Doctor of Medicine, Department of Pathology, College of Medicine Soonchunhyang University Hospital, Seoul, Korea 3 Doctor of Medicine, Department of Radiology, College of Medicine Soonchunhyang University Hospital, Seoul, Korea Corresponding author: Tae H Lee, Department of Internal Medicine, SoonChunHyang University Hospital, 657 Hannam Dong, Yongsan Gu, Seoul 140-743, Korea. Email: [email protected]

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Figure 1. Imaging studies of tailgut cyst carcinoid tumour. (a) Colonoscopy reveals that a huge mucosal elevated lesion, more than 4 cm in size, is seen at 5 cm above the anal verge in the rectum. (b) EUS shows a huge anechoic cyst with homogeneous hypoechoic contents outside the rectal wall (mucosa and muscularis mucosae) (white arrow). (c) T1-weighted MR imaging demonstrates a wellcircumscribed cystic mass, about 5 cm in size, with low signal intensity (white arrow). (d) T2-weighted MR imaging demonstrates a well-circumscribed cystic mass with high signal intensity (white arrow).

the chest and abdominal radiological examinations were also normal. On colonoscopy, a huge mucosal elevated lesion, more than 4 cm in size, was seen at 5 cm above the anal verge (AV) in the rectum (Figure 1(a)). EUS showed that the lesion was a huge anechoic cyst with homogeneous hypoechoic contents outside the rectal wall (Figure 1(b)). Pelvic MRI axial imaging revealed an approximately 5  4.6  6.2 cm3 sized well-circumscribed non-enhancing cystic mass, with high signal intensity in T1-weighted imaging (Figure 1(c)) and intermediate signal intensity in T2-weighted imaging in the right lateral wall of the rectum, which preserved the adjacent tissues (Figure 1(d)). Based on the imaging findings, the possibility of a duplication cyst was considered in the differential diagnosis.

(Figure 2(a)). Microscopic findings demonstrated a unilocular cystic mass. Its wall was composed of thick fibrous and smooth muscle tissue. The inner lining cells were denuded in most areas, and its content was amorphous eosinophilic granular material mixed with hemosiderin macrophages. Multiple foci of a characteristic organoid pattern, seen in well-differentiated neuroendocrine tumours, such as trabeculae or ribbons of monotonous cuboidal cells, could be identified in the cyst wall (Figure 2(b)). Each tumour cell had a central round nucleus with salt-and-pepper type chromatin. The tumour cells exhibited a diffuse strong positive reaction for chromogranin A (Figure 2(c)), synaptophysin and CD56. The Ki67 proliferation index was 4%. A focus of residual pseudostratified cuboidal epithelium was noted without any direct transition to the former mass (Figure 2(d)).

Treatment The patient underwent a transanal excision of the rectal mass to confirm the diagnosis and to remove the mass.

Pathologic examination On section, the mass was found to be a unilocular cyst filled with chocolate-coloured muddy material

Outcome, prognosis and follow-up The final diagnosis was a rectal carcinoid tumour arising within a tailgut cyst. One month after operation, the patient was found to have residual mass in the rectum; he was carefully monitored by regular checkups with radiological examination because he refused additional surgery, and his postoperative course was

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Figure 2. Pathologic findings of a carcinoid tumour with a tailgut cyst. (a) A unilocular cyst, measuring 6.5 cm in the greatest dimension, is filled with red-brown chocolate-coloured muddy material. (b) There is multifocal proliferation of uniform small round cells in ribbons or cords (a: H-E,  100). (c) The tumour cells are strongly positive for chromogranin A. (Chromogranin A,  100). (d) Most lining cells were denuded with a residual focus of pseudostratified cuboidal epithelium (H-E,  200).

satisfactory for more than two years, without progression.

Discussion This case highlights the diagnostic challenges of the carcinoid tumour arising within a tailgut cyst in a male patient. First, the diagnosis is usually delayed due to the extreme rarity of carcinoid tumour with tailgut cysts. To the best of our knowledge, only 17 cases of carcinoid tumours arising within a tailgut cyst have been reported to date, almost all of them in females, and only four cases in male patients have been reported.3 The incidence of retrorectal lesions, including tailgut cysts, is also difficult to establish because there have been few large series published, but it is estimated at one in 40,000 based on Mayo Clinic data.4 Second, the presentation of carcinoid tumour with tailgut cysts is usually non-specific and is most frequently related to the compressive effects of a growing pelvic mass.5 The most common symptoms are pain and constipation followed by rectal fullness and urinary difficulty. To date, carcinoid tumours with tailgut cysts have not been reported to produce the symptom

complex of carcinoid syndrome, so it is very difficult to have a high index of suspicion for carcinoid tumour with tailgut cysts before surgery. Finally, other retrorectal cysts including rectal duplication cysts, cystic sacrococcygeal teratomas, epidermal cysts, epidermoid cysts and pyogenic abscess can occur in the retrorectal space. It is difficult to distinguish the imaging appearance of a tailgut cyst from that of many other retrorectal cysts. The radiologic findings of tailgut cysts show a discrete, well-marginated, multilocular presacral mass with water or soft-tissue density, depending on the contents of the cyst in computed tomography (CT).6 The MRI findings typically show low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.7 However, substantial overlap exists in the imaging findings of presacral cysts; therefore, histopathologic analysis is essential to establish a definitive diagnosis of carcinoid tumour with a tailgut cyst.7 In addition, the pathogenesis of carcinoid tumour arising within a tailgut cyst is still unclear. A previous study reported that this tumour origin might be a hormone-associated phenomenon.8 As there was female predominant tendency in a carcinoid tumour with a tailgut cyst carcinoid tumour, Liang et al.8

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considered the possibility of a female hormone, and strong estrogen receptor immunoreactivity found in most patients with these tumours.

Declaration of conflicting interests None declared.

Contributorship

Conclusion A carcinoid tumour arising within a tailgut cyst is very rare, even in male adults, and is often difficult to distinguish from other retrorectal cysts. Because tailgut cysts have a potential of malignant transformation, unlike most retrorectal cysts, histological conErmation of suspicious tailgut cyst lesions is essential for diagnosis. Complete excision of the carcinoid tumour with tailgut cysts with free surgical margins is the treatment of choice and prognosis for patients with these tumours is generally favourable.

Learning points 1. The carcinoid tumours arising within tailgut cysts are very rare and usually found in middle-aged females. 2. For diagnosis, imaging studies including CT, MRI are helpful, but have some limit to distinguish other retrorectal cysts; therefore, diagnosis thorough histological examination should be performed. 3. Complete excision of the carcinoid tumour containing the tailgut cyst with free surgical margins is the treatment of choice. Prognosis for this tumour depends on the status of complete surgical resection.

The work was carried out in collaborations among all authors. JHK wrote this article and THL helped review article and with alteration. S-YJ provided pathological analysis and pictures. SSH performed review of radiologic images.

References 1. Hjermstad BM and Helwig EB. Tailgut cysts. Report of 53 cases. Am J Clin Pathol 1988; 89: 139–147. 2. Mathis KL, Dozois EJ, Grewal MS, et al. Malignant risk and surgical outcomes of presacral tailgut cysts. Br J Surg 2010; 97: 575–579. 3. Charalampakis V, Stamatiou D, Christodoulakis M, et al. A large presacral tailgut cyst with a carcinoid tumor in a male: report of a case. Surg Today. Epub ahead of print 10 January 2013. DOI: 10.1007/s00595-012-0482-4. 4. Jao SW, Beart RW, Spencer RJ, et al. Retrorectal tumors. Mayo Clinic experience, 1960–1979. Dis Colon Rectum 1985; 28: 644–652. 5. Mathieu A, Chamlou R, Le Moine F, et al. Tailgut cyst associated with a carcinoid tumor: case report and review of the literature. Histol Histopathol 2005; 20: 1065–1069. 6. Johnson AR, Ros PR and Hjermstad BM. Tailgut cyst: diagnosis with CT and sonography. AJR Am J Roentgenol 1986; 147: 1309–1311. 7. Yang DM, Park CH, Jin W, et al. Tailgut cyst: MRI evaluation. Am J Roentgenol 2005; 184: 1519–1523. 8. Liang JJ, Alrawi S, Fuller GN, et al. Carcinoid tumours arising in tailgut cysts may be associated with estrogen receptor status case report. Int J Clin Exp Pathol 2008; 1: 539–543.

Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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A carcinoid tumour arising within a tailgut cyst: a diagnostic challenge.

A 49-year-old man was referred with constipation that had lasted for a few months. On colonoscopy, a subepithelial tumour more than 4 cm in size was s...
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