Unilateral isolated extraocular muscle lymphoma.

Area of Science:

• Ophthalmology
• Oncology
• Pathology

Background:

• Ocular adnexal lymphomas are rare, with mucosa-associated lymphoid tissue (MALT) lymphomas being the most common subtype.
• Isolated involvement of a single extraocular muscle by MALT lymphoma is an unusual presentation.

Observation:

• A 59-year-old woman presented with a 3-month history of progressive diplopia and a swollen upper eyelid.
• Imaging revealed a mass originating from the left superior rectus muscle without bone erosion.
• Histological examination confirmed infiltration by small lymphoid cells.

Findings:

• The patient was diagnosed with Stage 1AE low-grade marginal zone B cell lymphoma.
• Differential diagnoses included Chlamydia psittaci infection and IgG4-related sclerosing disease.
• Initial treatment with doxycycline was ineffective.

Implications:

• Localized radiotherapy (30 Gy) achieved excellent clinical and radiological resolution.
• This case highlights the importance of considering MALT lymphoma in the differential diagnosis of isolated extraocular muscle masses.
• Successful treatment with radiotherapy suggests its efficacy in managing this rare presentation.