Large esophageal schwannoma: En-bloc resection with primary closure by esophagoplasty⋆

Highlights • Gastrointestinal schwannomas are submucosal tumors accounting for 2–7% of mesenchymal gastro-intestinal neoplasms.• Esophageal schwannomas are more frequent in women, and are usually located in the upper to mid portion.• Symptomatic esophageal schwannomas can be excised entirely, with low rate of recurrence and favorable overall outcomes.• Large esophageal schwannomas resulting in dilated proximal segment, esophagoplasty should be considered for defect closure.


Introduction
Esophageal tumors are seldom benign, and around 1% are detected clinically and radiologically [1]. The most frequently encountered are leiomyomas [1], and represent around 80% of benign esophageal tumors [2]. Esophageal schwannomas, on the other hand, are exceedingly rare, and constitute less than 2% of all esophageal tumors [3]. Esophageal schwannomas are initially described by Chaterlin and Fissore in 1967 [4]. Schwannomas are neurogenic tumors present within the mediastinum [1]. While hav- ing odynophagia, dysphagia, and/or shortness of breath as common presenting symptoms [1], esophageal schwannomas may be incidentally detected [5]. We hereby present the first reported case of a huge benign schwannoma located within the thoracic portion of the esophagus, for which complete excision of the mass and closure through an esophagoplasty was successfully performed. The present work has been reported in accordance with the SCARE criteria [6].

Case presentation
A 50-year-old healthy lady, case of bilateral partial mastectomy for high grade ductal carcinoma in situ, presented in 2014 with progressive exertional dyspnea, with minimal dysphagia to solid food, over a period of several years.
An enhanced CT scan of the chest revealed a well-defined soft tissue mass arising from the proximal third of the esophagus, measuring 7.8*5.4*10.5 cm in its maximal transverse, AP, and   CC dimensions, respectively, with prominent superior mediastinal lymph nodes, the largest measuring 7 mm (Fig. 1). An upper gastrointestinal endoscopy with ultrasound showed an elevated smooth surface lesion at around 20 cm from the incisors, originating from the submucosa, abutting the muscularis mucosa, and covered by a hypervascularized mucosa (Fig. 2).
Through a right posterolateral thoracotomy incision, the pathological portion of the esophagus was identified. The proximal portion of the esophagus was dilated due to the chronic partial obstruction caused by the mass.
Enucleation of the mass was impossible as the layer between the mucosa and submucosa could not be developed safely. Taking advantage of a dilated esophageal segment proximally, en bloc excision of the tumor was performed preserving enough width of esophageal wall. The width of the remaining esophagus measured 8 cm uniformly along the 15 cm longitudinal defect caused by the tumor excision. The 8 cm width allowed the reconstruction of the 15 cm longitudinal defect of the esophagus without undue narrowing of the lumen (Fig. 3). The esophagus was closed in two layers using a 3-0 vicryl running suture for the mucosa and 3-0 Polydioxanone (PDS) for the muscular layers. (Fig. 4).
Grossly, a 9.5*7.0*3.0 cm firm mass, covered with normal mucosa having a focal ulceration, was identified (Fig. 5). The mass is tan-white, pale, and homogeneous, with neither necrotic nor hemorrhagic areas. Microscopically, the tumor was composed of   revealed a diffuse positivity for S-100 (Fig. 6D), focally positive SMA, and negative staining for CD34, CD117, and Desmin, respectively. This confirmed the diagnosis of a benign esophageal schwannoma. All lymph nodes in the resected specimen were negative.
Gastrograffin swallow, performed five days later, revealed no evidence of contrast leak. Diet resumed, gradually thereafter, and advanced as tolerated. She was discharged home after a smooth postoperative course. The patient has been followed up for approximately 4 years, without any evidence of recurrence nor complications.

Discussion
Esophageal schwannomas are categorized under neurogenic tumors. The latter are classified according to Ranson's histopathological classification, published in 1940, as either nerve sheath tumors or neuroblastic tumors of the sympathetic system [7]. Schwannoma is the most common peripheral nerve sheath tumor. It usually occurs solitary and very rarely in the gastrointestinal tract [7].
Among the most common malignancies in the esophagus are the squamous cell carcinomas. Tumors that originate from mesenchymal cells, such as leiomyomas, leiomyosarcomas, gastrointestinal stromal tumors, and schwannomas, are uncommon inside the esophagus [8,9].
Schwannomas of the esophagus are frequently developed more in females than males, with a ratio of 4 to 1 [10], especially during the 5th to 6th decade of life. There is a strong predominance of this disease in Asian population, with most of reported cases from Asian institutions, in the world literature. The youngest reported case of esophageal schwannoma, by Choo et al was in a 22-yearold Asian American male, complaining of dyspnea with progressive dysphagia [11]. These tumors are frequently located in the upper to mid esophageal portion, within the mid mediastinum. So far, 98 cases of esophageal schwannomas are reported in the world literature (Appendix 1-Supplementary material).
Schwannoma of the gastrointestinal tract are submucosal tumors, commonly covered by normal mucosa and principally involving the submucosa and the muscularis propria [12]. Histologically, esophageal schwannoma portrays either Antoni A and/or B pattern(s) [1], and are characterized by peripheral lymphoid cuffing, benign nuclear atypia, and spindle-shaped cells [13]. Bundles of S-100 protein-positive spindle cells are intermixed in a fibrous, S-100 protein negative, background. They express negative expressions for smooth muscle markers such as actin, desmin, CD117(c-kit), and CD34. Hematoxylin and eosin staining reveals fascicular arrangement of spindle cells with palisading cell nuclei [5]. A preoperative including radiologically-alone diagnosis of this entity is difficult to achieve, and often established, after surgical resection [13].
As a rule, most benign mesenchymal tumors of the esophagus arise from the submucosa layer, and can be enucleated without destruction of the internal mucosa, and with preservation of good swallowing function. On the contrary, malignant neoplasms generally require more extensive resection and reconstruction; so the pre-emptive diagnosis is important in decision making, before any definitive treatment is undertaken [8].
Enucleation, using either video-assisted thoracoscopic surgery or endoscopically, is becoming the approach of choice for small submucosal tumors, measuring less than 2 cm in length [13,14]. Recently, robotic-assisted enucleation for a large esophageal schwannomas is made possible [15]. However, for large tumors, usually those greater than 8 cm with broad areas adherent to the muscularis layer, the resultant mucosal defect, upon resection, becomes extensive. In such scenarios, segmental esophagectomy, followed by esophagogastrostomy, are the preferred surgery of choice [16], as direct anastomosis is considered difficult. In general, any growing mass with symptoms are indications for surgical resection. As such, no cut off size of the tumor is mentioned in the literature. If it is noted as high grade on biopsy or more than 10 cm in size, the appropriate therapy is en-bloc esophagectomy with tumor-free resection margin, because those will carry malignant potentials [17].
Esophageal schwannomas can significantly increase in size, reaching up to 15 cm, as reported in the literature, without severe symptoms of dysphagia and dyspnea. In such extreme cases, there isn't significant narrowing of the esophageal lumen or compression on the trachea. Variation in surgical approach is evident in the literature and depends mainly on the size and extent of the lesion. Simple lesion enucleation, segmental esophagectomy with primary anastomosis, or even subtotal esophagectomy with gastric pull-up or jejunal/colonic interposition are some of the surgical options. The originality in our report is that esophagoplasty as an option for repair of a large esophageal defect after en bloc resection of an esophageal schwannoma should be considered if the esophagus is dilated along the length of the tumor. The width of the remaining esophageal wall at the site of the tumor excision should be at least 7-8 cm to allow a longitudinal closure that should restore the normal caliber of the esophagus which is around 1.5-2.5 cm in diameter [18].
Malignant transformation, albeit rare in esophageal schwannomas, is indicated by the more frequent mitotic figures, necrosis, and cytological irregularities [1]. When malignancy is suspected, radical surgery is indicated, including esophagectomy and lymph node dissection, to avoid any recurrence or distant metastasis [1].
Finally, the prognosis with benign schwannomas of the gastrointestinal tract, after complete resection, is usually excellent [7], with dismal rate of recurrence.

Conclusion
Esophageal schwannomas are rare submucosal lesions that carry very low malignant potentials. While small lesions are amenable for enucleation using minimal invasive procedures, larger tumors, especially those greater than 8 cm, may request en-bloc esophagectomy. In cases where the proximal esophageal segment is dilated, resection followed by esophagoplasty for defect closure should be considered.