Immunohistologic analysis of small lymphocytic infiltrates of the orbit and conjunctiva.

In a prior study we reported that monotypic immunoglobulin expression significantly correlated with an increased risk of dissemination by small lymphocytic infiltrates (SLIs) of the orbit and conjunctiva. However, less than half of all monotypic SLIs disseminated. In this study, we applied a large panel of monoclonal antibodies to cryostat sections of orbital and conjunctival SLIs to address two questions. First, might immunohistologic results other than immunoglobulin staining predict which patients with monotypic SLIs will develop disseminated lymphoma? Second, what is the usefulness of these findings in the diagnosis of orbital and conjunctival SLIs? We found that immunohistologic results did not significantly predict or correlate with disseminated lymphoma in patients with monotypic SLIs, either at time of presentation (ie, staging evaluation positive) and/or subsequently. However, three monotypic infiltrates (10%) had a proliferative rate (Ki-67-positive) of 20% or greater, and all three cases disseminated. Regarding the usefulness of the antibody panel, a B to T cell ratio of 4 or greater (76%), anomalous pan-T cell antigen expression by B cells (38%), and pan-B cell antigen loss (15%) were found exclusively in monotypic SLIs. Combining these results, 80% of monotypic SLIs had additional immunophenotypic criteria of lymphoma. Thus, these findings appear to be useful, although less helpful than immunoglobulin staining, and provide another means of immunophenotypic diagnosis when the results of immunoglobulin staining are technically unsatisfactory or difficult to interpret. We were unable to detect anomalous antigen expression or antigen loss in polytypic infiltrates, including one lesion which locally recurred 30 months later as a histologically indistinguishable, clearly monotypic SLI. We attribute the absence of these findings in polytypic SLIs to their relatively infrequent occurrence in monotypic infiltrates and/or to our inability to detect small clones of malignant cells (if present) by our immunohistologic methods.