Tailgut cysts: diagnostic challenge for both pathologists and clinicians

Abstract

Retrorectal area is a well-known space for the presence of some familiar lesions, like “sacrococcygeal teratoma” in children and a low-grade malignant tumor called “chordoma” in adults. However, a variety of congenital, inflammatory, and neoplastic lesions can occur in this area, but not famous enough to the practicing pathologist to be easily familiar with. Retrorectal cystic hamartoma or “tailgut cyst” is one of them. It is a benign, developmental lesion. In addition to its nonspecific and misleading clinical presentation, it can also confuse the pathologist while giving the definitive diagnosis. Patients who had multiple, unnecessary operations before the correct diagnosis was made had been reported in the literature. The largest series of 53 cases was collected over a 35-year period by Hjermstad and Helwig at the Armed Forces Institute of Pathology, Washington, DC, USA. Unfortunately, 51 out of 53 cases were not given the correct initial diagnosis of tailgut cyst. However, most of the pathologists were aware of that they were dealing with a benign, congenital, cystic process but had difficulty in further classifying it. A 37-year-old Turkish woman was admitted to our hospital with 3 months history of weakness in her legs with an accompanying low back pain. Her medical history included an appendectomy performed approximately 20 years ago and two cesarean sections. The transrectal ultrasound showed a well-defined cystic mass with dense internal echoes in the posterior rectal area, measuring 3.5×2.5 cm. Partial, minimal lobulation was identified in its posterior part. MRI revealed a well-circumscribed cystic lesion in the presacral area at the level of lower sacrum and coccyx. Another hypodense anococcygeal cyst was also identified. The left half of the sacrum showed hypoplasia. The patient had undergone an operation with the preoperative diagnosis of rectal duplication cyst based on the radiological findings. Both cysts were excised completely. Frozen section just revealed a benign simple cyst. Gross examination showed that both cysts are thin-walled and the larger one measures 3 cm in its maximum diameter. Cyst fluid was clear in appearance. Microscopically, different types of epithelium were identified lining the cyst walls. The cysts are mostly composed of stratified squamous epithelium and ciliated columnar epithelium, but low cuboidal to flat epithelium was also present. Fibrofatty tissue was seen in the underlying stroma with accompanying focal, mild mononuclear inflammatory cell infiltrate. No remarkable specific tissue fragments were identified in the wall, like bundles of well-formed smooth muscle fibers, adnexal elements of the skin, neural elements, and heterologous mesenchymal tissue, like cartilage or bone, which are all important in the differential diagnosis. The final diagnosis was a tailgut cyst. Developmental cysts of the retrorectal area are classified according to their origin and histopathological features as epidermoid cyst, dermoid cyst, enteric or rectal duplication cyst, cystic teratoma, and tailgut cyst. The precise nature of the tailgut cysts remains controversial. Middledorpf is believed to be the first author to consider that tumors of the retrorectal area are probably derived from remnants of the postanal intestine. In 1953, Hawkins and Jackman Int J Colorectal Dis (2007) 22:1283–1285 DOI 10.1007/s00384-006-0153-2