Lymphoid hyperplasia of the orbit and ocular adnexa: A clinical ​pathologic review.

Lymphoid hyperplasia (LH) is a benign lymphoproliferative disorder that, in a minority of cases, may be associated with concurrent or metachronous non-Hodgkin lymphoma. LH cases are further subdivided into "reactive" and "atypical" categories based on the presence or absence of unequivocal malignant features. With improving molecular diagnostic technologies, "reactive" LH is by far the most common category of LH, with atypical LH accounting for only a small minority of specimens. Similarly, lesions previously diagnosed as LH are now being revised as low-grade B-cell non-Hodgkin lymphoma or diagnosed as newly described benign conditions such as IgG4-related disease. Additional differential diagnoses include specific and nonspecific orbital inflammations, infiltrative processes, and depositions. Hence, there are emerging changes in the patterns and proportions of entities that fall within the spectrum of lymphoproliferative disorders of the orbit and ocular adnexa. Reactive LH and low-grade malignant lymphoproliferative disorders in the orbit and ocular adnexa are clinically and radiologically indistinguishable from each other, requiring tissue biopsy in all cases. The prognosis of ocular adnexal LH is generally favorable, but the small risk of non-Hodgkin lymphoma mandates follow-up for at least 5 years. We summarize the current state of knowledge on LH occurring in the orbit and ocular adnexa.