Retrorectal tumor: a case report of a patient with "schwannoma".

INTRODUCTION

Injuries that affect the presacral space are rare, and are part of a heterogeneous group of entities of primary concern to colorectal surgeons. These lesions are located in anatomically difficult area to be addressed, hence the need for prior surgical planning, as well as knowledge of the major diseases that affect this region.

The incidence of these lesions varies from 1: 40.000 to 1: 630,000[7], being more common in females between 40 and 60 years[8].

CASE REPORT

Man of 94 years showed changes in bowel habits few months ago. Digital rectal examination showed solid pelvic mass with no apparent invasion of the rectal mucosa; it is not possible to predict its upper limit. Computed tomography of the pelvis showed solid-cystic lesion in proximity to the sacrum bone and rectum, with apparent cleavage plane between adjacent structures (Figure 1). He underwent transperitoneal resection of the lesion. Major bleeding occurred during surgery, which was controlled, requiring blood transfusion with four blood cell concentrate units.

Figure 1.

Tumor images located in the presacral space

Postoperative was without morbidity and discharged on the 7th day after surgery. The pathology confirmed it was schwannoma of low-grade without evidence of malignancy (Figure 2).

Figure 2.

Encapsulated tumor (10 cm in diameter - A) and open aspect (B) showing mucoid material inside

DISCUSSION

Although most retrorectal lesions are congenital, most patients do not have a previous positive family history; the most common clinical presentation is asymptomatic mass found to proctologic examination[5]. The retrorectal masses are palpable on rectal exam by up to 97% of cases[7].

Due to the angular change caused by the puborectalis muscle mass patients often have changes in bowel habits with a tendency to constipation, feeling of incomplete evacuation or thin stools.

A flexible sigmoidoscopy is useful for viewing the invasion of the rectal mucosa by the tumor and its upper limit, for correct surgical management.

Imaging tests are essential for accurate diagnosis, and the MRI is superior to CT in the characterization of pelvic masses for the presence of bone invasion or neural involvement[2].

Treatment is mainly surgical. Many of these injuries, despite the benign appearance, may contain malicious elements or potentiality for malignant degeneration in the medium term, and the risk of infection in benign cysts. This patient was discharged on the seventh postoperative day, with uneventful recovery.

The resection of the coccyx is not recommended unless there is suspicion of involvement by malignant disease[3]. As far as rectum is often densely adhered to the tumor, should be carried out careful dissection, to avoid injury.

There are three types of surgical approach: anterior or abdominal transperitoneal or extra-peritoneal, conventional or laparoscopic access; the posterior approach; and combined abdominosacral route.

The anterior approach is used for high lesions (with caudal end until the level S4) without evidence of sacral engagement. The rectum is folded laterally and the median sacral artery is usually linked with the dissection and tumor is enucleated[2].

The latter approach is preferred for smaller, benign lesions that do not extend beyond the level S4. This route is used when the presence of neural involvement or for better viewing and preservation[1].

Tumors of major proportions exceeding proximal and distal S4 level are more easily operated via abdominosacral[2] route. The resection can be performed synchronously with the patient in the lateral position or sequentially with the change in position after each stage of the operation. The benefit of the combined approach includes the ability to display structures such as ureter, nerve and sacral iliac vessels, particularly important in cases where there is the need to perform partial sacrectomy, especially in chordoma.

The adjuvant therapies have only a secondary role in the management of tumors in retrorectal space. In cases where radical surgery is contraindicated, palliative radiotherapy has been carried out, except for chordoma, classically radioresistant.

The survival of benign tumors approaches to 100% in most studies[7]. However relapse is not uncommon. Development of cysts relapses up to 15%[1]. Approximately 9-45% of retrorectal malignant tumors are most commonly solids than cystic, with recurrence rates of 45%; five year survival rate is about 8 to 17%.