Extranodal marginal zone B-cell lymphoma involving superior rectus muscle: A clinicopathological case report.

A 66-year-old female had suffered from proptosis in the left eye (OS) and double vision for 1 month due to abnormality of the superior rectus muscle. Visual acuity was noted as 20/20 in both eyes (OU). Eye movement showed limited OS supraduction. Magnetic resonance imaging revealed an indistinct mass in the orbit involving the superior rectus muscle. A biopsy specimen of the orbital tumor led to the histological diagnosis of extranodal marginal zone B-cell lymphoma. Radiotherapy with a total dosage of 30 Gy was administered, which subsequently resolved the tumor. However, the supraduction limitation of ocular movement remained unchanged. Supraduction limitation is due to muscular contraction disorder of the superior rectus muscle, caused by direct lymphoma cell invasion.