Presentation
Swelling of the left eye.
Patient Data
The largely extraconal mass lesion in the left orbital floor with low signal on T1 and T2-weighted images, and homogeneous contrast enhancement. The involvement of the inferior rectus muscle, orbital septum, lower lid, and the adjacent conjunctiva also is seen.
Case Discussion
The mass was resected and sections show monotonous proliferation of small-sized and centrocytes lymphatic cells admixed with a few monocytoid lymphocytes. The presentation of these cells around perineural space and within stratified muscle fibers are seen. Mitotic figures are scant.
IHC:
LCA: Diffusely positive.
Ki67 index: 15-20%.
CD20: Diffusely positive.
CD3: a few dispersed positive.
CD5: a few dispersed positive.
CD10: Negative
BCL2: Positive.
Cycline D1: Negative.
Diagnosis: Low-grade B-cell lymphoma, Mucosa-associated lymphoid tissue lymphoma(MALToma).
Primary lymphoma of the orbit is one of the commonest orbital tumors and accounts for as much as half of all orbital malignancies. It is a B-cell non-Hodgkin lymphoma, and in most cases arises from mucosa-associated lymphoid tissue (MALT).