Simultaneous intravascular large B‑cell lymphoma and papillary thyroid carcinoma: A case report.

Intravascular large B-cell lymphoma (IVLBCL) is a rare subtype of B-cell lymphoma. The concurrence of IVLBCL and papillary thyroid carcinoma (PTC) is extremely rare. A 63-year-old woman was diagnosed with double-expression IVLBCL that presented as a hemophagocytic syndrome, complicated by PTC. IVLBCL was diagnosed by positron emission tomography/computed tomography (PET/CT) before bone marrow biopsy. Immunofixation electrophoresis displayed M proteins positive and IgG kappa light chains that the differential diagnosis should have included both multiple myeloma and IVLBCL. After treatment with rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, prednisone and etoposide, the patient's cytokine titres and other laboratory indicators returned to normal. PET/CT showed that complete remission had been achieved. She has been taking zanubrutinib for 1.5 years and remains in remission. This is a report of a patient with hemophagocytic syndrome-associated IVLBCL with CCND1 and DNMT3A gene mutations combined with PTC and describes changes before and after treatment.