Introduction to a Unique Presentation

Clinicians recently identified a unique case involving a 59-year-old man with progressive, painless right blepharoptosis over three months. This condition initially appeared as simple poor levator function, yet imaging revealed a much more complex pathology. Magnetic resonance imaging (MRI) demonstrated isolated enlargement of the right levator palpebrae superioris (LPS). Crucially, the superior rectus and other extraocular muscles remained unaffected. This specific finding served as the sole harbinger for primary orbital lymphoma.

Diagnostic Imaging and Histopathology

The radiological evaluation provided essential clues for the diagnosis. The enlarged muscle appeared isointense on both T1 and T2-weighted images. Furthermore, it showed homogenous contrast enhancement and a low apparent diffusion coefficient (ADC) on diffusion-weighted MRI. These imaging characteristics often suggest hypercellularity, which is typical of lymphoid tumors. To confirm the diagnosis, the medical team performed an incisional biopsy via an upper lid skin crease incision. The histopathology revealed a low-grade B-cell non-Hodgkin lymphoma. Specifically, the immunophenotype was consistent with extranodal marginal zone lymphoma, a common subtype of primary orbital lymphoma.

Management of Primary Orbital Lymphoma

Systemic staging is vital for patients diagnosed with orbital malignancies. In this case, staging showed no extraorbital disease, confirming the localized nature of the tumor. Consequently, the patient proceeded with localized orbital radiotherapy. At the 3-month follow-up, the patient achieved complete resolution of the ptosis and the muscular enlargement. This outcome underscores the importance of early detection through advanced imaging. Moreover, it highlights that isolated muscle involvement, while rare, must remain on the differential diagnosis list for orbital masses.

Clinical Significance of Diffusion-Weighted MRI

The authors of this case emphasize the critical role of diffusion-weighted MRI (DWI) when investigating single muscle enlargement. Low ADC values are particularly suggestive of lymphoma because the high cellular density restricts water diffusion. While thyroid eye disease or idiopathic orbital inflammation more commonly cause muscle enlargement, clinicians should maintain high suspicion for primary orbital lymphoma when imaging displays these specific characteristics. Therefore, localized radiotherapy remains a highly effective treatment for these marginal zone B-cell lymphomas.

Frequently Asked Questions

How does primary orbital lymphoma typically present?

It often presents as a painless, slowly progressive mass or swelling in the orbit. In rare cases, it can cause isolated muscle enlargement leading to symptoms like ptosis or double vision.

Why is Diffusion-Weighted MRI important for orbital tumors?

Diffusion-weighted MRI helps differentiate between various orbital lesions. A low apparent diffusion coefficient (ADC) indicates high cellularity, which strongly points toward a diagnosis of lymphoma rather than inflammation.

What is the standard treatment for localized orbital marginal zone lymphoma?

Localized low-dose radiotherapy is the standard treatment and usually results in excellent local control and high rates of complete resolution.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice. Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Agarwal A et al. Isolated levator palpebrae superioris enlargement as the sole harbinger of primary orbital lymphoma. Orbit. 2026 Apr 08. doi: 10.1080/01676830.2026.2654187. PMID: 41949897.

Valvassori GE, et al. Lymphoma of the orbit and adnexa. Neuroimaging Clin N Am. 1996;6(1):137-54.

Polito E, et al. Primary adnexal B-cell lymphomas: a clinical and prognostic study of 17 cases. Graefes Arch Clin Exp Ophthalmol. 2002;240(10):837-44.