Submucosal tunneling endoscopic resection for a rectal schwannoma: A rare case

Abstract

Rectal Schwannomas are exceptionally uncommon tumors that arise from the peripheral nerve plexus. These neoplasms are incidentally discovered as submucosal tumor-like lesions during routine colonoscopy in individuals without symptoms. Surgical resection accompanied by biopsy is considered the standard approach for diagnosis and treatment. We describe here the first successful utilization of submucosal tunneling endoscopic resection (STER) technique for removal of a rare rectal Schwannoma. A 59-year-old asymptomatic female was found to have a 15 × 12 mm submucosal tumor during colonoscopy. Submucosal tunneling endoscopic resection achieved en bloc resection and pathology confirmed Schwannoma. The patient was discharged uneventfully with no adverse events. This study highlights the efficacy and safety of STER for removing rare rectal Schwannomas.

Introduction

Schwannomas are slow-growing, nonmalignant tumors that arise from Schwann cells in peripheral nerves. ¹ While they are uncommon in the gastrointestinal tract, comprising about 2–6% of nonepithelial tumors, ² they can still develop in this area. The gastrointestinal tract predominantly harbors Schwannomas in the stomach (83%), while such tumors are exceptionally rare in the rectum. ² Schwannomas are incidentally detected as a submucosal tumor (SMT)-like lesion during routine endoscopy or abdominal imaging conducted for unrelated reasons. ² A conclusive diagnosis is established by carefully analyzing the surgical specimen through pathological examination.

The preferred treatment for rectal Schwannomas is controversial given their extremely low prevalence. ³ The submucosal tunneling endoscopic resection (STER) technique, also known as the “nonexposed” full-thickness endoscopic resection method, has been applied for the treatment of cardia achalasia and SMTs originating from the muscular propria layer in the upper gastrointestinal tract. ⁴ By creating a submucosal tunnel for lesion removal, the preservation of mucosal integrity can be achieved, effectively reducing the risk of perforation. ⁵ This study presents the first report of the successful application of the STER technique for resecting a rare case of rectal Schwannoma and conforms to CARE guidelines. ⁶

Case report

An asymptomatic 59-year-old female underwent a routine screening colonoscopy and was incidentally found to have an SMT in the rectum. The patient had no significant medical history to report. Consequently, the patient was referred to our hospital (the Affiliated Jinhua Hospital, Zhejiang University School of Medicine) for further assessment on February 19, 2024. Endoscopic ultrasound (EUS; Olympus, Tokyo, Japan) confirmed the presence of a heterogeneously hypoechoic mass measuring approximately 15 × 12 mm, which originated from the muscular layer (Figure 1A and B). These findings suggest compatibility with a gastrointestinal stromal tumor (GIST). Subsequent abdominal enhanced CT and pelvic magnetic resonance imaging both identified the presence of a well-enhanced, round-shaped mass in the rectum, with partial protrusion of the lesion outside the rectal lumen (Figure 1C and D).

Figure 1.

(A) Colonoscopy showed a smooth-surfaced submucosal mass in the rectum; (B) EUS the presence of a heterogeneously hypoechoic mass measuring approximately 15 × 12 mm, which was originated from the muscular layer. (C and D) abdominal CT and pelvic MRI both identified the presence of a well-enhanced, round-shaped mass in the rectum, with partial protrusion of the lesion outside the rectal lumen. EUS, endoscopic ultrasound; CT, computed tomography; MRI, magnetic resonance imaging.

After obtaining the informed consent from the patient, she underwent STER with monitored anesthesia care. The procedure involved a standard gastroscope (GIF-260z), a VedKnife (D-type, 1.5 mm, Vedkang Medical, Changzhou, China), and a VIO 200 D (Erbe, Tübingen, Germany). The submucosal lift was achieved by injecting a mixture of saline solution and indigo carmine. A precise horizontal incision was made 3 cm proximal to the lesion, allowing for the creation of a submucosal pocket (Figure 2A). After carefully enucleating the tip of tumor, the intramuscular portion of the tumor was dissected using a VedKnife. Dissection was carried out until reaching the perirectal fat level, with vigilant attention to preserve the integrity of the tumor capsule (Figure 2B and 2C). An en bloc resection of the tumor was achieved (Figure 2D and 2E), and the mucosal defect was closed (Figure 2F) with multiple metal clips (Microtech, Nanjing, China). Antibiotic prophylaxis was applied for 3 days, and the patient was uneventfully discharged. No adverse event was encountered.

Figure 2.

(A) A precise horizontal incision was made 3 cm proximal to the lesion, allowing for the creation of a submucosal pocket; (B and C) dissection of the tumor was carried out until reaching the perirectal fat level; (D and E) an en bloc resection of the tumor was achieved; (F) the mucosal defect was closed with multiple metal clips.

Pathological analysis revealed the presence of spindle cells in the tumor, characterized by minimal nuclear heterogeneity. Immunohistochemical staining supported the diagnosis of a Schwannoma, with positive results for S-100 and negative results for CD34, CD117, and SMA (Figure 3).

Figure 3.

Pathology finding and immunohistochemical staining of the tumor. (A) s-100(+), (B) CD34(-), (C) CD117(-), (D) SMA(-).

Ethical approval for publication was obtained from the Medical Ethics Committee of the Affiliated Jinhua Hospital, Zhejiang University School of Medicine. Written informed consent for the publication of anonymized information was obtained from both the patient and her authorized representative.

Discussion

Schwannomas, originating from Schwann cells and commonly affecting peripheral nerves in adults, are rarely found in the gastrointestinal tract. ⁷ Predominantly occurring in the stomach and small intestine, gastrointestinal Schwannomas are exceptionally rare in the rectum.^1,2 During colonoscopy, colorectal Schwannomas can manifest as submucosal masses or yellowish polypoid changes, and EUS may reveal hypoechoic masses originating from the lamina propria. Preoperative diagnosis of colorectal Schwannomas consistently poses challenges as they need to be distinguished from other mesenchymal tumors.^7,8 Therefore, a definitive diagnosis still relies on histopathology and immunohistochemistry, with positive S-100 staining being characteristic of Schwannomas.

Schwannomas are generally benign, though malignant transformation can occur on rare occasions. A systematic review of 93 colorectal Schwannomas found three malignant cases (3.2%), highlighting the infrequency of this transformation. ² Complete surgical resection with clear margins has historically been the preferred treatment.^2,9 However, colorectal surgery inevitably involves risks of postoperative complications, including surgical site infection, anastomotic leakage, stoma-related problems, anastomotic bleeding, and long-term issues such as bowel and sexual dysfunction. ¹⁰ Notably, surgical site infection is the most frequent, resulting in higher patient morbidity, longer hospital stays, readmission, mortality, and considerable economic costs. ¹¹ Interestingly, a prior study indicated that Butyrylcholinesterase levels may serve as a potential predictive marker for surgical site infection. ¹² To date, the optimal treatment approach for Schwannomas remains uncertain, ¹³ and there is a scarcity of data regarding endoscopic resection of colorectal Schwannomas.^14,15 The emergence of STER technique offers a less invasive alternative to surgical procedures for subepithelial tumors in the upper gastrointestinal tract. Originally developed for the upper gastrointestinal tract, the STER technique offers advantages such as flexibility, safety, efficiency, and minimal invasiveness. Currently, there are only three documented case reports demonstrating its successful application in achieving complete R0 resection of rectal GISTs.^3,16,17 To the best of our knowledge, this case represents the first successful attempt for removal of a rare rectal Schwannoma using STER technique. In the case of SMTs originating from the muscular layer, endoscopic full-thickness resection may be required to remove both the muscular layer and the serosa. ¹⁴ Although most cases of perforation can be effectively repaired using various endoscopic suture methods, achieving complete closure through this technique can be difficult, occasionally resulting in postoperative complications, including severe infection. Perforation in the extraperitoneal middle and lower rectum typically does not result in complications such as infectious peritonitis. Nevertheless, improper management can cause pelvic infection around the rectum or even lead to retroperitoneal and lower limb infections due to the loose pelvic tissues and their communication with the retroperitoneal space and lower limb fascia space.

Applying the STER technique for resecting rectal Schwannomas originating from the muscular layer helps maintain intact mucosa, minimizing the risk of infection and complications resulting from full-thickness resection-induced perforation. Our experience supports the safety and efficacy of STER as a curative treatment for this rare rectal neoplasm. However, additional prospective studies with larger cohorts are required to further validate this technique.

Conclusions

This case report highlights the successful application of STER for the removal of a rare rectal Schwannoma in a 59-year-old asymptomatic female. The procedure was effective in achieving en bloc resection without any adverse events, demonstrating its potential as a safe and viable alternative to traditional surgical methods. The findings suggest that STER can be considered for similar cases, particularly for SMTs with challenging locations. Future studies with larger patient cohorts are necessary to validate these results and further establish the role of STER in the management of rectal Schwannomas and other SMTs.