Journal of Cancer Research and Therapeutics

: 2019  |  Volume : 15  |  Issue : 1  |  Page : 258--260

A well-differentiated neuroendocrine tumor (Grade I) arising in a tailgut cyst

Angad Singh1, Swapnil Karnik2, Bhushan Khedkar2, Sanjay Deshmukh3, Kedar Deodhar1,  
1 Department of Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India
2 Department of Pathology, Ruby Hall Clinic, Pune, Maharashtra, India
3 Department of Surgical Oncology, Ruby Hall Clinic, Pune, Maharashtra, India

Correspondence Address:
Dr. Kedar Deodhar
Department of Pathology, 8th Floor, Annexe Building, Tata Memorial Hospital, Dr. E Borges Road, Parel, Mumbai - 400 012, Maharashtra


Tailgut cysts are rare congenital lesions presenting as retrorectal space masses. They can occur in all age groups. Patients often present with ill-defined nonspecific symptoms and the diagnosis if often delayed. Malignancy arising in a tailgut cyst is an even rarer and unique occurrence. A precise diagnosis can be made only after complete excision and histopathological examination of the retrorectal space mass. We describe here a case of a 63-year-old male presenting with chronic constipation, who was diagnosed with a well-differentiated neuroendocrine tumor (Grade I) arising in a tailgut cyst after surgical excision.

How to cite this article:
Singh A, Karnik S, Khedkar B, Deshmukh S, Deodhar K. A well-differentiated neuroendocrine tumor (Grade I) arising in a tailgut cyst.J Can Res Ther 2019;15:258-260

How to cite this URL:
Singh A, Karnik S, Khedkar B, Deshmukh S, Deodhar K. A well-differentiated neuroendocrine tumor (Grade I) arising in a tailgut cyst. J Can Res Ther [serial online] 2019 [cited 2020 Jun 4 ];15:258-260
Available from:

Full Text


Tailgut cysts (also known as retrorectal cystic hamartomas, retrorectal cyst, and cyst of postanal intestine) are congenital lesions occurring in the retrorectal space. Tailgut cysts are believed to arise from remnants of embryonic hindgut.[1] During embryological development between 28 and 35 days gestational age, the embryo develops a true tail into which there occurs an extension of the embryonic hindgut. This caudal extension is termed as tailgut.[1],[2] Failure of regression of the embryonic hindgut results in the development of a tailgut cyst.[1] Tailgut cysts usually present with ill-defined symptoms such as constipation, rectal bleeding, and perianal pain and can occur in all age groups, more commonly in middle-aged females.

Malignancy arising in a tailgut cyst is very rare; however, there can be the development of tumors such as adenocarcinoma, neuroendocrine tumors (carcinoid), squamous cell carcinoma, endometrioid carcinoma, and sarcomas.[3],[4],[5] Till now, about 16 cases of neuroendocrine tumors arising in tailgut cysts have been reported.[4],[6],[7],[8] We present an unusual case of a well-differentiated neuroendocrine tumor (Grade I) arising on a background of a tailgut cyst.

 Case Report

A 63-year-old male presented with constipation for the past 10 years. Radiological studies showed a large mass in the retrorectal space. Fine-needle aspiration cytology (FNAC) from the mass was done and showed sheets and clusters of oval and short spindle hyperchromatic cells showing palisading and attempt at acinar formation. A possibility of an epithelial neoplasm was suggested. A core biopsy was then done which showed a neoplasm composed of small round cells along with connective tissue. A differential diagnosis of an epithelial/myoepithelial neoplasm/papillary ependymoma/skin adnexal lesion was thought of. Surgery was done and a 7 cm × 5 cm × 4 cm retrorectal mass weighing 92 g was excised (R0 resection). On cut surface, the mass was soft, gray-white, solid. No hair, cartilage, or any other structure was identified on gross examination. Histological examination showed predominantly a circumscribed neoplasm composed of tumor cells arranged in acini, nests, and trabecular patterns [Figure 1]. Connective tissue fragments were seen in between the nests of tumor cells. Tumor cells were small round to oval with hyperchromatic nuclei and inconspicuous nucleoli. At the periphery, small foci of benign squamous lining and benign columnar epithelial lining were seen at few places [Figure 1] and [Figure 2]. On immunohistochemistry, tumor cells were positive for synaptophysin [Figure 3] and cytokeratin, whereas negative for chromogranin, glial fibrillary acidic protein, SMHC, p63, and CD56. Ki-67 (Mib-1) proliferation index was <1%. A diagnosis of a well-differentiated neuroendocrine tumor (Grade I) arising in a tailgut cyst was made.{Figure 1}{Figure 2}{Figure 3}


The retrorectal space is bounded anteriorly by rectum and posteriorly by sacrum. The superior border is formed by peritoneal reflection, laterally by ureters and iliac vessels, whereas the inferior boundary is formed by levator ani and coccygeus muscles. Many nonneoplastic and neoplastic lesions occur in this space ranging from cystic lesions (developmental cysts: Dermoid, epidermoid, and tailgut cysts; duplication cysts: Meningoceles) to solid lesions (chordomas, teratomas, and adrenal rest tumors).[4],[5] Tailgut cysts are usually multiloculated and lined by a variety of epithelia, most commonly squamous, glandular, and transitional epithelia.[1] All cases of tailgut cysts should be carefully assessed for the presence of any concurrent malignancy, most commonly adenocarcinoma followed by carcinoid tumors. Till now, about 16 cases of neuroendocrine tumors arising in tailgut cysts have been reported.[4],[6],[7],[8] The age group ranged from 18 to 62 years, more commonly in females. Grossly, most of the lesions were multiloculated cystic with only a single case showing tan-white lobulated parenchyma. Microscopically, all cases exhibited classical histopathological patterns of neuroendocrine tumors such as trabeculae, ribbons, festoons, and nests of tumor cells.[4]

Our patient is an elderly male who underwent surgical excision of a retrorectal mass. Grossly, the mass was solid, soft, gray-white. Microscopy revealed an overgrowth of tumor cells present in acini, nests, and trabecular patterns with only peripheral lining of squamous and columnar epithelium. The patient is alive on follow-up after 2 years.

Imaging is not accurate to detect malignancy, and a precise diagnosis can be made only after surgical resection and complete and careful histopathological examination.[5] While grossing an excised retrorectal mass, it is important to sample all different looking areas to exclude malignancy. FNAC and core biopsies are often not sufficient to form an accurate diagnosis, primarily due to sampling issues.[1] Therefore, in conclusion, a high index of suspicion should be kept for accurate diagnosis of malignancies arising in tailgut cysts.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Hjermstad BM, Helwig EB. Tailgut cysts. Report of 53 cases. Am J Clin Pathol 1988;89:139-47.
2Campbell WL, Wolff M. Retrorectal cysts of developmental origin. Am J Roentgenol Radium Ther Nucl Med 1973;117:307-13.
3Au E, Anderson O, Morgan B, Alarcon L, George ML. Tailgut cysts: Report of two cases. Int J Colorectal Dis 2009;24:345-50.
4Mathieu A, Chamlou R, Le Moine F, Maris C, Van de Stadt J, Salmon I. Tailgut cyst associated with a carcinoid tumor: Case report and review of the literature. Histol Histopathol 2005;20:1065-9.
5Chhabra S, Wise S, Maloney-Patel N, Rezac C, Poplin E. Adenocarcinoma associated with tail gut cyst. J Gastrointest Oncol 2013;4:97-100.
6Prasad AR, Amin MB, Randolph TL, Lee CS, Ma CK. Retrorectal cystic hamartoma: Report of 5 cases with malignancy arising in 2. Arch Pathol Lab Med 2000;124:725-9.
7Spada F, Pelosi G, Squadroni M, Lorizzo K, Farris A, de Braud F, et al. Neuroendocrine tumour arising inside a retro-rectal tailgut cyst: Report of two cases and a review of the literature. Ecancermedicalscience 2011;5:201.
8Wöhlke M, Sauer J, Dommisch K, Görling S, Hinze R. Rare case of a primary metastatic carcinoid tumour arising in a tailgut cyst. Virchows Arch 2009;455:S390.