Lymphomas
of the orbit may arise spontaneously, or may be associated with the
development of systemic lymphoma. These
lesions may cause a painless, unilateral proptosis (#22128) or may
manifest as a salmon patch- like thickening protruding into the
conjunctiva.Histopathologically,
it may be difficult to differentiate malignant lymphoma from a lymphoid
hyperplasia.Lymphomas
characteristically show a diffuse monotonous infiltrate of atypical
lymphocytes (#22129).There
is minimal vasculature, no follicles, and no mixture of other cell types
such as plasma cells.Benign
lesions tend to show a mixture of cells, increased vascularity, and
formation of follicles or germinal centers.The definitive diagnosis histopathologically often requires fresh
tissue for surface staining.Lymphomas
show monoclonal staining and are predominantly B cells (#22131).A typical lymphoid hyperplasia will show a mixture of B and T cells
and will be polyclonal.
