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1 April 2015 - Case of the Week #347

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Case of the Week #347

Clinical History:
A 46 year old woman had a stomach mass, which was biopsied.

Micro images:


What is your diagnosis?































Diagnosis:
Schwannoma of stomach

Discussion:
The tumor is well circumscribed and surrounded by lymphocytes with germinal centers. It consists of with interlacing bundles of spindle cells and collagen. At other sites, Schwannoma is typically biphasic, with compact hypercellular Antoni A areas containing Verocay bodies and myxoid hypocellular Antoni B areas with thickened hyalinized vessels. However, stomach tumors typically are not biphasic and lack Verocay bodies. The tumor cells are narrow, elongated and wavy with tapered ends. They may also display degenerative nuclear atypia (ancient change).

Schwannoma is rare in the GI tract. It occurs most frequently in the stomach, but still only at 1/50 the incidence of GIST tumors. Schwannomas originate from nerves with a Schwann cell sheath. As in this case, they are usually benign, slow growing and asymptomatic, but may cause bleeding, pain or a palpable mass.

Immunohistochemistry may be useful, as Schwannomas are positive for S100 and vimentin and negative for cKit / CD117, CD34 and SMA. The differential diagnosis includes GIST tumors, which are CD117+ and CD34+, S100- and vimentin-. Leiomyomas are SMA+ and S100-.

Excision is usually curative, with low recurrence rates (Hippokratia 2012;16:280, Case Rep Surg 2012;2012:280982).


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