Obturator masses have a certain probability of occurrence in pelvic tumors. The most common origins of obturator masses are neurological tumors, including schwannoma and neurofibroma (1–3). Local tumors around the lateral obturator zone have been reported to be potentially resectable by laparoscopic lateral pelvic tumor dissection (LLPTD) (4). However, only a limited number of studies have assessed and confirmed the safety and operability of such tumors (4). Careful inspection of CT and MRI is important to determine the tumor positioning preoperatively. The tumors, locating in the retroperitoneal space, may be close to iliac vessels, obturator nerve and even spermatic cords (1,2,5). In order to gain better exposure for tumor dissection, exploratory transperitoneal laparoscopy has usually been performed to treat affected cases (4). Resection of the tumor was carefully performed to ensure the safe removal of the specimen with complete and functional preservation of the iliac vessels and obturator nerve (2,6,7). In particular, cross-obturator masses may be technically demanding due to the requirement for sufficient operative space. The aim of the present study was to introduce a technique modification with the combination of the laparoscopic approach and hand-assisted (HA) open surgery for patients with large obturator masses.

The present study reported on the use of a novel operation procedure for coping with trans-obturator tumor, combining laparoscopic with open approaches. Due to the limitation of obturator obstruction and operation space, laparoscopic surgery alone is not able to fully dissociate obturator tissue to reach the tumor area below the obturator. In order to ensure the overall removal of the tumor, the most appropriate method used in the present study is to push the tumor to the area above the obturator for laparoscopic dissection. This procedure requires open surgical assistance. Compared with traditional open surgery, the present method utilizes minimally invasive laparoscopic surgery and fine dissection with fewer complications for fast recovery, and due to these advantages, it may be is deemed more appropriate than the usual clinical approach to meet the patient's clinical requirement.

A total of 186 articles were retrieved by searching the PubMed database for studies published between January 13, 2006 and December 20, 2019 using the search term ‘mass in obturator’. Publications were included in the review if they met the following list of preset inclusion criteria: i) The mass was located in the obturator fossa; ii) the mass was a solid tumor based on surgical biopsy diagnosis or imaging diagnosis; iii) lymph node or tumor metastasis was excluded. A total of 17 publications, mainly case reports, were included in the review of the present study. A total of 6 cases were diagnosed as obturator nerve schwannoma (2,6–10) and 1 case was a malignant schwannoma of the obturator nerve treated with neoadjuvant chemotherapy followed by neurosurgery (1). Other types of tumor (1 case each) included retroperitoneal extragonadal germ cell tumor (5), pelvic angiomatosis (11), parasitic leiomyoma (12), neurofibroma (3), presacral lipoma (13), aggressive angiomyxoma (14), mucoid pseudocyst of the obturator nerve (15), thigh abscess mistakenly diagnosed as sarcoma (16), fibroblastic osteosarcoma (17) and desmoid tumor (18). The patients' characteristics are summarized in Table III. From the previous studies and the present study, data on the cases of obturator tumor were extracted and further analyzed based on composition ratio and are presented in Table IV and Fig. 4. The majority of the cases were benign (~75%) and originated from neural tissue (~50%). The selected operative approach was either open or minimally invasive (50% each).

Laparoscopic surgery provides surgeons with a clear and magnified view of the operative field (19). Therefore, it is useful for complex surgical procedures, particularly in deep locations in the narrow lateral pelvic space (4,14). It appears that only a limited number of studies have explored surgical dissection of obturator masses and these lacked systematic conclusions (2,5).

LLPTD, as a minimally invasive pelvic surgical technique, has been applied in the clinical setting due its feasibility and reduced associated blood loss (4). However, the effect of the limited space must be taken into consideration. In the present case, occupation of the obturator fossa by a large tumor made LLPTD more difficult. The combined open approach with HA-LLPTD allows experienced LLPTD surgeons to modify the tumor location and perform complete tumor dissection without any complications (14).

This approach may be performed via surgical cooperation and without the requirement for an assistant port (1). LLPTD combined with an open approach has been previously reported (14,20). Surgeons must have a comprehensive anatomical understanding to use this approach. The technique reported in the present study included LLPTD combined with the open method for pelvic and inguinal surgery, and it appears to be more useful for such cases as compared with the conventional approach.

Obturator nerve injury is the most common surgical complication reported in the literature (6,15). The reasons are as follows: i) The combination of sharp and blunt dissection of the tumor causes injury to the nerve, as it is situated in close proximity to the tumor; ii) tumor tissue may be dissected along with the obturator nerve, irrespective of whether the nerve is infiltrated by the tumor; iii) pelvic lymph node dissection may cause injury. It is noteworthy that caution should be taken intraoperatively to protect the nerve against mechanical and thermal injury; in addition, the treatment process should include close observation of perioperative symptoms and signs, postoperative follow-up and neurotrophic support (1,3).

Recent studies have reported on cases of SFT located in the pelvic region (21,22). However, to the best of our knowledge, SFTs spanning the obturator fossa with involvement of obturator nerve have not been reported to date. SFTs may be misdiagnosed as other tumor types occurring in this area, such as neurological tumors. Furthermore, the assessment of malignancy should incorporate the biological behavior of the tumor and not rely on histopathological examination alone. Atypical SFTs may undergo malignant transformation and recurrence (23). Therefore, a rigorous follow-up is crucial for assessing the efficacy of surgical treatment.

Several types of tumor have been reported to be located in the obturator fossa, the majority of which are benign, mainly derived from neurological and mesenchymal tissues (7,12). In particular, obturator nerve schwannoma is more commonly reported compared with other types. The operative approach may be either open or minimally invasive (1,6,7,9). However, in recent years, robotic and laparoscopic surgery have become mainstay surgical options (6,8). In the present case, a combined approach was used to treat a transobturator tumor, which appeared to be the optimal choice.

HA-LLPTD allows experienced laparoscopic surgeons to safely perform complete resection of tumors located in the obturator fossa with fewer complications. The combination of laparoscopic and open surgery is an innovative method for the excision of obturator foramen masses, which provides clinical solutions for extracting tumors of the obturator region. Although the short-term outcome appears to be favorable, due to the small sample size, further investigations with larger sample sizes are still required to assess and explore the long-term outcome of this approach.