Rheumatologic evaluation showed a slightly elevated antinuclear antigen level. A regimen of parenteral methotrexate sodium with low-dose prednisone led to temporary resolution of the proptosis and chemosis. Three months later, the patient again developed proptosis in the right eye, a pupil-sparing oculomotor nerve palsy with hypotropia in the right eye, and exotropia. A biopsy specimen of a palpable anterior orbital nodule disclosed a dense lymphohistiocytic infiltrate without overt angiocentricity or hypervascularity. There were small lymphocytes with clumped chromatin, round to irregular nuclear contours, and scant cytoplasm admixed with occasional larger, atypical lymphocytes with complex nuclei and moderately abundant clear cytoplasm (Figure 2). The larger, atypical lymphocytes were marked as T cells by using CD2, surface CD3, and CD45RO but demonstrated loss of other T-cell markers CD5 and CD7, indicative of an aberrant T-cell population. CD4 and CD8 staining were both present on small lymphocytes, but a specific pattern on the large atypical lymphocytes was difficult to interpret. Immunostains for Epstein-Barr virus latent membrane protein and CD56 were negative. There was insufficient tissue for additional stains such as CD30 or cytotoxic markers. Polymerase chain reaction gene rearrangement studies of both paraffin-embedded biopsy specimens were inconclusive owing to insufficient DNA quantity or quality. However, on the basis of tumor morphologic characteristics and aberrant loss of T-cell antigens, a diagnosis of peripheral T-cell lymphoma was rendered.