Local recurrence as extraocular muscle lymphoma after 6 years of chronic myositis: a case report

Background Extraocular muscle is usually affected by thyroid disease or inflammatory pseudotumor, but seldom by neoplastic process. Primary malignant lymphoma involving isolated extraocular muscle is very rare, especially after 6 years of chronic myositis. Case presentation A middle-aged female presented with swelling of the lower lid of the right eye for 2 months. Magnetic resonance imaging showed significant enlargement of the right inferior rectus muscle belly. The patient first presented 6 years prior with upper eyelid swelling. A total of 5 surgical biopsies of the right eye were performed during 6 years with the following successive findings: inflammatory pseudotumor, chronic inflammation, inflammatory lesions, IgG4-related ophthalmic disease, and lastly, extraocular muscle extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Conclusion MALT lymphoma may have occurred as a result of chronic extraocular myositis. Malignancy should be considered in patients with recurrent painless extraocular muscle hypertrophy. Differential diagnosis can rule out thyroid-associated ophthalmopathy (TAO), whose symptoms are similar. Diagnosis confirmation by biopsy is warranted if necessary.