A 44-year-old woman presented with a submucosal rectal mass found incidentally during a physical examination. On digital rectal examination, the mass was soft with a smooth surface and was located on the left posterior wall of the rectum. The results of routine laboratory tests were all within the normal range. The patient underwent colonoscopy with endoscopic ultrasonography (EUS), but EUS-guided needle biopsy was deferred to avoid the risk of tumor seeding or infection in the pelvic cavity. The ultrasound showed a multilocular hypo- and anechoic 20-mm mass on the posterior wall of the rectum, which exhibited clear boundaries. Some of the tissue had calcified, and there was no internal blood flow. Only the cyst wall was enhanced by contrast during contrast-enhanced ultrasonography (CE-US) (Fig. 1).
On contrast-enhanced pelvic computed tomography (CT), the multilocular cystic lesion had a diameter of approximately 32 mm and was without enhanced solid components or calcification (white arrowhead). Blood was supplied to the lesion from the middle sacral artery (white arrow). There were no signs of lymph node metastasis (Fig. 2).
The finding of contrast enhancement of the cyst wall on magnetic resonance imaging (MRI) led us to suspect that the mass was strongly adhered to the left rectal wall (white arrows). The MRI also showed non-enhancing cystic components accompanied by solid components (white arrowhead) (Fig. 3).
The presumptive diagnosis was retrorectal tailgut cyst, and we decided to perform a laparoscopic tumor resection because we could not exclude the possibility of malignancy.
At laparoscopy, there was no evidence of liver metastasis or peritoneal dissemination. The capsule wall was free along the fascia propria of the rectum and could be seen in the left posterior wall of the rectum, free along the dorsal side of the tumor to the caudal side of the tumor (Fig. 4). The blood supply from the middle sacral vessels was divided and ligated with clips. An area of sclerosis along the tumor at the lateral rectum, which appeared to be the wall of the capsule, was breached during the resection, and a small amount of intestinal content was leaked. The pelvic cavity was copiously irrigated to prevent contamination. The tumor resection boundary was revised to completely remove the tumor, and the posterior and left side walls of the rectum were then reapproximated and repaired with eight stitches of 3–0 absorbable suture. Repeated checks for leaks were negative, but the digital rectal examination revealed a weakness in the rectal wall, which was secured by two additional stitches. The total interoperative blood loss was 270 mL, and the operation time was 368 min. The patient’s postoperative recovery was uneventful, and she was discharged without incident on postoperative day 7. Defecation dysfunction persisted for 2 months after surgery, but it subsequently resolved spontaneously.
Macroscopically, the tumor measured 43 × 35 × 10 mm and contained multiple cysts of different sizes, which contained white mucinous contents. Histologically, the inner surfaces of the cysts were smooth and even and the cyst walls were composed of smooth muscle, glial fibers, nerves, blood vessels, and fat. The immunohistochemical examination showed that the lesion had biphasic properties, containing tubular sweat gland-like structures composed of secretory cell-like cells as well as S100-positive myoepithelial cell-like cells, suggesting that the lesion contained eccrine sweat glands (Fig. 5). Cytokeratin (CK) 7, CK20, C-KIT, and adipophilin immunostaining were all negative, and the final diagnosis was a mature teratoma.