Schwannoma is a rare tumor of nerve origin that develops at the expense of Schwann sheath cells [1]. This tumor is distributed ubiquitously in the body [2]. Located in the digestive tract, together with leiomyomas, leiomyosarcomas and leiomyoblastomas, it constitutes the group of GIST (Gastro-Intestinal Stromal Tumor) [1] and the gastric site is predominant [3]. The clinical presentation is not very specific, ranging from palpation of an abdominal mass to the picture of bowel obstruction. Medical imaging, in particular computed tomography and magnetic resonance imaging associated with digestive endoscopy, make it possible to approach the diagnosis which will be confirmed by the immunohistochemical analysis of the operative part with, among other elements, a strong positivity to the anti-PS100 antibody [4]. Treatment is surgical and involves complete excision of the lesion with healthy resection margins [5]. The prognosis is generally favorable, although cases of malignant transformation have been reported in the literature [6,7].

The rarity and risk of malignant transformation of this affection prompted us to report this observed case to the visceral surgery department of the University Hospital Center de Libreville.

OBSERVATION

Mrs. EOS, 58 years old, with a history of bilateral ovarian cystectomies more than 10 years ago, had consulted for cessation of materials and gas with abdominal pain and bloating. The clinical examination on arrival revealed an occlusive syndrome with a scar from the median infraumbilical laparotomy. The unprepared abdomen (PSA) X-ray showed hail-like water-aeric levels. The complete blood count (CBC) had shown hyperleukocytosis at 11900 / mm3 predominantly neutrophilic. The blood ionogram was normal. Abdominal computed tomography could not be performed due to lack of resources. The hypothesis of a probable occlusion on flanges was retained as the first intention indicating an exploratory laparotomy. Via the midline extending the old scar, exploration of the peritoneal cavity revealed a large rounded hyper-vascularized mass of about 20 centimeters long axis, well circumscribed, developed at the expense of the small intestine in its ileal part and located 50 centimeters from the ileocecal junction (Figure 1). 

Figure 1: Vue per opératoire. Masse tumorale volumineuse hyper-vascularisée d’origine iléale indiquée par la flèche jaune. (Source personnelle : Dr DYATTA MAYOMBO Kévin).

This mass was obstructive and the slender upstream handles were dilated. The liver was macroscopically healthy and there was no mesenteric lymphadenopathy. A carcinological resection with a safety margin of 5 centimeters on either side of the mass had been performed with the mesenteric fan opposite. An end-to-end ileo-ileal anastomosis was made, followed by lavage and then drainage of the peritoneal cavity. The post-operative consequences were simple. The patient was discharged in the 10th postoperative period. Histological analysis of the surgical specimen revealed a proliferation composed of spindle-shaped cells arranged in a swirling bundle with rare nuclear palisades with little dysplasia and healthy section margins in favor of a low-grade schwannoma (Figure 2). 

Figure 2 : Vue microscopique. Cellules fusiformes disposées organisées en palissade (type A d’Antoni) évoquant un schwannome. (Source personnelle : Dr DYATTA MAYOMBO Kévin)

The immunohistochemical study revealed a strong positivity of the anti-PS 100 antibody, thus confirming the schwannoma. The control abdominal CT scan performed at 3 months was unremarkable.

Schwannomas are nerve sheath tumors that develop at the expense of Schwann cells. They are ubiquitously distributed and can affect any part of the body [8]. Concerning the digestive tract, it is necessary to know how to distinguish schwannomas from other gastrointestinal stromal tumors (leiomyosarcomas, leiomyomas, leiomyoblastomas) in which they represent 2 to 6% of cases [4,9]. Most digestive tract schwannomas are gastric in origin, but rare cases of colon, rectum, esophagus and small intestine have been reported [1,10].

In decreasing order of frequency, they affect the stomach (50 to 60%), the small intestine (20 to 30%) the colon (10%), the rectum, the esophagus (5%) and the abdomen (5%). The incidence is almost similar in men and women, with an average age between the 6th and 7th decades [1,9,10]. In the event of digestive impairment, the clinical picture of schwannomas may be that of a palpable abdominal mass of varying degrees of pain, upper gastrointestinal bleeding, transit disorder or even tenesmus; but at the extreme, it can be a true occlusion of the small intestine [4,9] by extrinsic compression or by obstruction as found in our case. The role of endoscopy in the diagnosis of these tumors is recognized by most authors, associated with computed tomography or even magnetic resonance imaging [11,12]. Faced with the picture of a probable bridle occlusion and the lack of means necessary to perform a CT scan, in our context, we suggested performing an exploratory laparotomy. From a therapeutic standpoint, complete surgical resection of the tumor with healthy margins is the recommended treatment, which our team carried out in front of this mass. We performed segmental ileal resection with end-to-end anastomosis at the same time. These tumors can reach 25 to 30 centimeters in diameter. Some teams recommend a combination of radiotherapy and / or chemotherapy, the benefit of which has not been formally established [5,9]. Histological analysis of the surgical specimen will confirm the diagnosis and distinguish the 2 types of schwannoma. Antoni type A which corresponds to compact areas of spindle cells, with a scant eosinophilic cytoplasm, arranged in palisades (Verocay nodules) and rolls, as in our case study, and Antoni type B which corresponds to spindle-shaped cells with a haphazard arrangement, rare, separated by a matrix stained heterogeneously with hematoxylin eosin and alcian blue (myxoid tissue) [3,9]. The diagnostic certainty is provided by the immunohistochemical study which will demonstrate a strong positivity to the anti-PS 100 antibody and vimentin [1,4,13]. Positive staining with the anti-PS 100 antibody confirms the nerve origin of the tumor [13]. The postoperative course of schwannomas is generally favorable and the prognosis is good. However, cases of recurrence and malignant transformation have been described in the literature [6,7] requiring at least annual monitoring over 5 years, with clinical examination and performing an abdominal tomodensitometry [13].

Schwannoma is a rare benign condition. Ubiquitous, it can be localized in the digestive tract, predominant in this case at the gastric level. Ileal involvement is poorly described. Treatment is based on complete surgical segmental resection of the lesion with safety margins. The immunohistochemical analysis of the part with the positivity for the ant-PS100 antibody makes the diagnosis. The good prognosis of this affection should not, however, overlook the potential risk of malignant transformation and impose monitoring.

Conflict of Interest

The authors declare no conflict of interest when performing this work. Patient consent and authorization from the appropriate authorities were required prior to the production of this work.

1. Prévot, S.et al. “Benign Schwannoma of the Digestive Tract: A Clinicopathologic and Immunohistochemical Study of Five Cases, Including a Case of Esophageal Tumor.” American Journal of Surgical Pathology, vol. 23, 1999, pp. 431–436.

2. Robert, R. Les Tumeurs Nerveuses Primitives Tronculaires des Membres: À Propos de 9 Cas. Thèse de médecine, Université de Nantes, 1997.

3. Bhardwaj, K.et al. “Rectal Schwannoma.” Indian Journal of Gastroenterology, vol. 21, 2002, pp. 116–117.

4. Miettinen, M.et al. “Schwannomas in the Colon and the Rectum: A Clinicopathologic and Immunohistochemical Study of 20 Cases.” American Journal of Surgical Pathology, vol. 25, 2001, pp. 846–855.

5. Arcidiaco, M.et al. “Schwannoma of the Rectum: Clinico-Therapeutic Study.” Minerva Chirurgica, vol. 36, 1981, pp. 267–272.

6. Catania, G.et al. “Malignant Schwannoma of the Rectum: A Clinical and Pathological Contribution.” Chirurgia Italiana, vol. 53, 2001, pp. 873–877.

7. Reinbold, W.D.et al. “Malignant Schwannoma of the Rectum.” Radiologie, vol. 36, 1996, pp. 663–666.

8. Stout, A.P. “The Peripheral Manifestations of the Specific Nerve Sheath Tumor (Neurilemmoma).” American Journal of Cancer, vol. 24, no. 4, 1935, pp. 751–796.

9. Miettinen, M.et al. “Gastrointestinal Stromal Tumours.” Annales Chirurgiae et Gynaecologiae, vol. 87, 1998, pp. 278–281.

10. Matsuki, A.et al. “Schwannoma of the Esophagus: A Case Exhibiting High 18F-Fluorodeoxyglucose Uptake in Positron Emission Tomography Imaging.” Diseases of the Esophagus, vol. 22, 2009, pp. E6–E10.

11. Stroh, C., and T. Manger. “Ultrasound Diagnosis of a Rare Retrorectal Tumor.” Zentralblatt für Chirurgie, vol. 128, 2003, pp. 1075–1079.

12. Vinhais, S.N.et al. “Schwannoma of the Esophagus: Computed Tomography and Endosonographic Findings of a Special Type of Schwannoma.” Acta Radiologica, vol. 45, 2004, pp. 718–720.

13. Tzu-Chun, L.et al. “An Infrequent Plexiform Variant of Schwannoma of the Glans Penis: A Rare Finding.” Asian Journal of Andrology, vol. 12, no. 3, 2010, pp. 455–457.