[A case of malignant lymphoma with a metastasis to the lateral rectus muscle]

We reported a 75-year-old woman with malignant lymphoma who had a metastasis to the right lateral rectus muscle. She was well until two months earlier, when a tumor in the left thigh began to enlarge. Ten days before admission, she noticed medial deviation of the right eyeball. Neurological examination showed the right esotropia with isolated paralysis of the right lateral gaze. She denied double vision. MR imaging demonstrated a swelling of the right lateral rectus muscle. Gallium scanning revealed abnormal accumulation in the right orbit and the left thigh. The tumor in the left thigh was histologically diagnosed as non-Hodgkin's lymphoma, diffuse large cell type. Discrete extraocular muscle metastasis is rare and unreported for malignant lymphoma. Reported cases of breast and thyroid cancers metastatic to the extraocular muscles did not develop diplopia similar to our case. The rapid growth of metastases to the extraocular muscles produces a large visual axes deviation, therefore no diplopia may be elicited.