BACKGROUND
Colonic schwannomas are rare benign neurogenic tumors originating from Schwann cells of the peripheral nerve sheath, and account for a very small proportion of gastrointestinal mesenchymal neoplasms. Their nonspecific clinical and radiological appearance often leads to diagnostic dilemma. Definitive diagnosis relies on histopathological and immunohistochemical evaluation. Preoperative diagnosis remains particularly challenging because colonic schwannomas may mimic other mesenchymal or cystic lesions, including gastrointestinal stromal tumors (GISTs) and duplication cysts.
CASE REPORT
We present the case of a 67-year-old asymptomatic male patient with a schwannoma of the transverse colon wall diagnosed only after surgical excision, through histopathological and immunohistochemical examination. After upper and lower endoscopy revealed no mucosal abnormalities, computed tomography suggested a duplication cyst, while magnetic resonance imaging favored a GIST arising from the transverse colon. Due to the uncertain preoperative diagnosis and the size and location of the lesion, transverse colectomy with primary anastomosis was performed. Histopathological examination demonstrated a spindle-cell tumor with very low mitotic activity and no necrosis. Immunohistochemistry showed positivity for S-100 and SOX10 and negativity for CD117, CD34, and DOG1, confirming the diagnosis of schwannoma. Complete R0 excision was achieved, and the patient remained recurrence-free 2 years later.
CONCLUSIONS
This case emphasizes the diagnostic challenge and the importance of considering schwannoma in differential diagnosis of colonic intramural masses extending into the transverse mesocolon. The predominantly intramural and exophytic growth pattern may account for both the normal endoscopic findings and the misleading radiological appearance. Complete surgical excision with negative margins is associated with an excellent prognosis for benign colorectal schwannomas.

Keywords: Colon, Transverse; Colorectal Neoplasms; Gastrointestinal Diseases; Peripheral Nerves; Schwann Cells