Pure intravascular recurrence of CD5-positive diffuse large B-cell lymphoma primarily arising from the nasal cavities

Background CD5-positive diffuse large B-cell lymphoma (DLBCL) and intravascular large B-cell lymphoma (IVL) are recognized as rare subsets of large B-cell lymphoma with poor prognosis. These two categories have similar clinicopathological features suggesting that they might overlap. Case presentation We present a case of a 72-year-old man with submental tumors. Positron emission tomography/computed tomography (PET/CT) showed tumors in the nasal and paranasal region and multiple submental and jugular swollen lymph nodes with abnormal uptake of 18 F-fluorodeoxyglucose (FDG). Histology of biopsy from nasal tumors showed diffuse infiltration of large lymphoid cells, which showed positive expressions for CD20, CD79a, CD5 and negative for CD3 on immunohistochemistry. Thus, a CD5-positive DLBCL was diagnosed. After administration of 8 cycles of R-THPCOP (rituximab, pirarubicin, cyclophosphamide, vincristine and prednisolone), complete remission was achieved. Eight months after the first chemotherapy dose, local recurrence occurred. After salvage chemotherapy, nasal and paranasal tumors and lymph node swelling disappeared on PET/CT images, although the patient suffered from respiratory disturbance. A random skin biopsy revealed IVL, which was consistent with intravascular recurrence of CD5-positive DLBCL. Bone marrow smears showed hemophagocytosis. Conclusion We present a rare case of primary CD5-positive DLBCL that relapsed as pure IVL after chemotherapy. Our case suggests that CD5-positive DLBCL is closely related to IVL.