Eosinophilic granulomatosis with polyangiitis (EGPA) is a systemic vasculitis characterized by eosinophilia and anti-neutrophil cytoplasmic antibody (ANCA) positivity, indicating immune dysregulation. Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, but CD56 expression in DLBCL is extremely rare. We report a case of CD56-positive DLBCL in a patient with a history of EGPA. A 55-year-old man with EGPA and bronchial asthma presented with a painless right cervical swelling. Imaging revealed a 3 cm deep cervical mass formed by fused lymph nodes. Excisional biopsy showed diffuse proliferation of large atypical lymphoid cells. Immunohistochemistry was positive for CD20, CD56, BCL-2, and BCL-6, and negative for CD3, CD5, CD10, CD30, EBER, and MUM-1. Flow cytometry confirmed CD19+, CD20+, κ > λ, and CD56+ phenotype, consistent with germinal center B-cell–type DLBCL. PET–CT demonstrated localized uptake (SUVmax = 4.25) without distant lesions, and bone marrow was uninvolved. The patient was diagnosed with stage IA, low NCCN-IPI DLBCL. Pola-R-CHP therapy was initiated, and the patient is currently undergoing treatment. CD56 expression in DLBCL is rare and may be associated with a germinal center phenotype; however, careful evaluation for malignancy is warranted in EGPA patients presenting with atypical lymphadenopathy.CD56 expression in DLBCL is rare but may indicate a germinal center phenotype and favorable prognosis. Coexistence of EGPA and lymphoma underscores the need for malignancy evaluation in EGPA patients with atypical features.
Mitate et al. (Thu,) studied this question.