Extramedullary plasmacytoma of the lateral rectus muscle.

Plasmacytoma is an uncommon presentation of plasma cell malignancy, especially in the absence of multiple myeloma. Orbital plasmacytomas generally originate from bone, although few cases in the literature report orbital extramedullary plasmacytomas. We present the case of a 68-year-old man found to have a solitary extramedullary plasmacytoma in the lateral rectus muscle without further evidence of multiple myeloma. This case demonstrates a rare presentation for such a malignancy, and a review of the literature highlights the importance of proper workup and close monitoring to rule out multiple myeloma to guide management.