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).