Diagnosis of Primary Splenic Flexure Schwannoma Before Surgery Based on Endoscopic-Ultrasound–Guided Fine-Needle Biopsy
Authors: Guru Trikudanathan, Sophia Smith, J. Shawn Mallery
Journal: Clinical Gastroenterology and Hepatology (2017)

A 60-year-old white woman with a history of hypertension, hyperlipidemia, and hypothyroidism presented with intermittent hematochezia for 1 month, with a stable hemoglobin level. Colonoscopy showed a 4-cm noncircumferential submucosal mass at the splenic flexure (Figure A), which on tunnel biopsy showed only colonic mucosa with prominent lymphoid aggregate. A contrast-enhanced computerized tomography of the pelvis showed a 3.5 × 2.4 × 2.5 cm ovoid, homogenously enhancing, exophytic mass in the posterior wall of the splenic flexure. A lower endoscopic ultrasound (EUS) confirmed a 3.5-cm hypoechoic mass arising from the muscularis propria (echogenic layer 4), which corresponded to the endoscopically visible submucosal mass located in the splenic flexure (Figure B). A transcolonic EUS-guided fine-needle biopsy was performed with 3 passes using a 22-gauge needle (Shark Core; Medtronic, Dublin, Ireland) in the presence of an onsite cytopathologist. Because the lesion was difficult to penetrate, 3 additional passes were made with a 19-gauge needle (Cook Medical, Bloomington, IN) with better penetration. Histopathologic examination using the H&E technique showed that spindle cells were present (Figure C). Immunohistochemistry showed that the tumor was diffusely positive for S-100, while immunonegative for CD117, smooth muscle actin, desmin, and CD34, consistent with schwannoma (Figure D). Magnetic resonance imaging of the abdomen and pelvis confirmed no metastatic lesions. The patient underwent a laparoscopic left-sided hemicolectomy. Histopathologic examination of the surgical specimen confirmed tumor-free resection margins and there was no neoplastic involvement in any of the 9 nodes examined. She was discharged a week after her surgery and was followed up on an outpatient basis with an unremarkable postoperative course for 6 months after surgery. Schwannomas are rare spindle-cell neoplasms of ectodermic origin arising from the neural sheath, which represents only 2% to 6% of all stromal tumors of the gastrointestinal tract.1Fotiadis C.I. Kouerinis I.A. Papandreou I. et al.Sigmoid schwannoma: a rare case.World J Gastroenterol. 2005; 11: 5079-5081Google Scholar, 2Nonose R. Lahan A.Y. Santos Valenciano J. et al.Schwannoma of the colon.Case Rep Gastroenterol. 2009; 3: 293-299Google Scholar Schwannomas of the gastrointestinal tract are not encapsulated, and thus distinctively are different from conventional schwannomas that arise in the central nervous system. They most frequently affect the stomach (83%) and small intestine (12%), whereas primary schwannoma of the colon unassociated with systemic neurofibromatosis is extremely rare.2Nonose R. Lahan A.Y. Santos Valenciano J. et al.Schwannoma of the colon.Case Rep Gastroenterol. 2009; 3: 293-299Google Scholar, 3Tashiro Y. Matsumoto F. Iwama K. et al.Laparoscopic resection of schwannoma of the ascending colon.Case Rep Gastroenterol. 2015; 9: 15-19Google Scholar Usually, schwannomas tend to be an incidental finding, with rectal bleeding or obstructive symptoms being reported very rarely.4Young P.E. Oosterveen S. Hanna N. et al.Presacral schwannoma diagnosed by EUS-guided FNA.Gastrointest Endosc. 2008; 67: 383-385Google Scholar Their diagnosis is based largely on surgically resected specimens.5Kudo T. Kawakami H. Kuwatani M. et al.Three cases of retroperitoneal schwannoma diagnosed by EUS-FNA.World J Gastroenterol. 2011; 17: 3459-3464Google Scholar EUS is a useful technique to characterize subepithelial lesions further, to ascertain the layer of tumor origin, as well as for procuring tissue for a conclusive diagnosis. When lesions are in or proximal to the sigmoid colon, it becomes particularly challenging to advance the echoendoscope to the left colon without direct visualization and perform EUS fine-needle aspiration using a conventional technique because most linear scopes have an oblique view. In our case, a primary schwannoma of the splenic flexure was diagnosed definitively by EUS-guided fine-needle biopsy after careful advancement of the echoendoscope to this region under endoscopic visualization. It is critical to review all available cross-sectional imaging of the pelvis to evaluate for redundant left colon and also to exclude large diverticuli before advancing the linear EUS scope. Advancing the scope under fluoroscopic guidance and water immersion techniques aid in safely negotiating the scope across a tortuous left colon, with the latter further aiding in visualizing smaller subepithelial lesions. Schwannomas are characterized by strong and uniform nuclear and cytoplasmic staining for S-100 staining and typically are immune-negative for c-kit, desmin, and smooth muscle actin. Cytomorphologic interpretation along with appropriate use of immunohistochemical markers enabled us to distinguish it from other spindle cell neoplasms. The exact biologic behavior of these tumors is unclear, although without resection there is a possibility of malignant degeneration.1Fotiadis C.I. Kouerinis I.A. Papandreou I. et al.Sigmoid schwannoma: a rare case.World J Gastroenterol. 2005; 11: 5079-5081Google Scholar, 2Nonose R. Lahan A.Y. Santos Valenciano J. et al.Schwannoma of the colon.Case Rep Gastroenterol. 2009; 3: 293-299Google Scholar, 6Çakır T. Aslaner A. Yaz M. et al.Schwannoma of the sigmoid colon.BMJ Case Rep. 2015; (bcr2014208934): 2015Google Scholar Radical excision with margins free of disease is the recommended therapeutic option because their response to chemotherapy and radiation is uncertain.6Çakır T. Aslaner A. Yaz M. et al.Schwannoma of the sigmoid colon.BMJ Case Rep. 2015; (bcr2014208934): 2015Google Scholar Thus, EUS-guided fine-needle biopsy was pivotal for an accurate preoperative diagnosis and appropriate management in our patient.