Diagnosis

Diagnosis

Schwannoma

Discussion

Schwannomas arise from Schwann cells in nerve sheaths and are usually sporadic and solitary. While they can occur anywhere in the body, schwannomas arising in the gastrointestinal tract are rare. When they do arise in the gastrointestinal tract, the majority occur in the stomach. These are submucosal lesions that generally arise from the myenteric plexus. They are slow growing and are often identified incidentally, but larger schwannomas may become symptomatic.

Histologically, schwannomas are characterized by two distinct patterns. Antoni A pattern consists of high cellularity with spindled cells that may demonstrate nuclear palisading, called Verocay bodies. This case included areas of significant Verocay body formation, as seen in figure 3. The Antoni B pattern, loosely distributed cells with myxoid stroma, was not seen in this case.

A specific feature of gastrointestinal schwannomas is a prominent surrounding lymphoid cuff, as seen in figure 4 of this case. This can help distinguish between other more common GI mesenchymal tumors, which lack this feature. Immunohistochemistry is very useful in making this diagnosis as well. S-100 is a sensitive and specific marker for schwannomas, which are generally negative for other GI mesenchymal tumor markers.

These tumors are generally benign and cured with resection. Malignant transformation only occurs in about 2% of cases.  Resection may be endoscopic or surgical depending on size. Diagnosis preoperatively may be difficult due to a lack of pathognomonic features on imaging.

References

Qi Z, Yang N, Pi M, Yu W. Current status of the diagnosis and treatment of gastrointestinal schwannoma. Oncol Lett. 2021 May;21(5):384. doi: 10.3892/ol.2021.12645.

Bohlok A, El Khoury M, Bormans A, et al. Schwannoma of the colon and rectum: a systematic literature review. World J Surg Oncol. 2018 Jul 3;16(1):125. doi: 10.1186/s12957-018-1427-1.

Mekras A, Krenn V, Perraki A, et al. Gastrointestinal schwannomas: a rare but important differential diagnosis of mesenchymal tumors of gastrointestinal tract. BMC Surg. 2018;18(1):47. doi: 10.1186/s12893-018-0379-2.

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