Temporal artery biopsy revealing marginal zone lymphoma in a patient with eosinophilic granulomatosis with polyangiitis

A 78-year-old man with a history of well-controlled eosinophilic granulomatosis with polyangiitis (EGPA) presented with sudden-onset right-sided monocular vision loss with elevated inflammatory markers, raising concern for giant cell arteritis. Right-sided temporal artery biopsy demonstrated a dense perivascular and perineural infiltrate of small clonal B cells (Fig. 1). Molecular studies confirmed a clonal immunoglobulin heavy locus rearrangement. A bone marrow biopsy demonstrated 30% involvement by the same process (Fig. 1). The patient was diagnosed with extranodal marginal zone lymphoma. Monocular vision loss in this patient was likely due to perineural infiltration of lymphoma or occlusion of the retinal artery and/or its branches by lymphoma cells. There are few reports of malignancy being diagnosed based on histology of a temporal artery biopsy [1]. None of the patients previously described had a pre-existing autoimmune disease. Non-Hodgkin’s lymphoma is known to be associated with autoimmune diseases, probably...