De Novo CD5-Positive Diffuse Large B-Cell Lymphoma: Report of a Case Presenting With Cutaneous Involvement and Featuring Extensive Intravascular Dissemination on Postmortem Examination.

De novo CD5-positive diffuse large B-cell lymphoma (DLBCL) represents 10% of DLBCLs and is frequently associated with an aggressive clinical course and poor response to chemotherapy. We report a case of an 84-year old man who presented with cutaneous lesions, malaise, and B-symptoms. A skin biopsy revealed neoplastic cells within the lumen of dermal vessels. The patient deteriorated rapidly and died. On postmortem examination, lymphadenopathy with diffuse effacement of lymph node architecture, widespread intravascular neoplastic cells in the skin, lungs, gastrointestinal tract, adrenal glands, testes, and kidneys; and rare, isolated neoplastic cells within vessels of liver and central nervous system were noted. Intravascular or intrasinusoidal invasion has been previously reported in earlier series of de novo CD5-positive DLBCL, but is not a widely recognized phenomenon, and requires differentiation from other lymphomas sharing this histopathologic feature.