RESUMO
Intravascular large B-cell lymphoma (IVLBL) is an uncommon form of non-Hodgkin lymphoma that is also known as malignant angioendotheliosis, intravascular lymphomatosis, and angiotropic large-cell lymphoma. The disease is characterized by a bizarre population of neoplastic cells, which are found systemically within vascular lumina. Although originally thought to be a neoplastic process of the endothelial cells, it has since been demonstrated, by molecular techniques and immunohistochemistry, that the neoplastic cells are of lymphoid origin. The differential diagnosis of these lesions includes granulocytic sarcomas that can be distinguished from IVLBL or other lymphomas by the presence of immunohistochemical positivity for myeloperoxidase. We describe a patient with a history of a myelodysplastic syndrome who subsequently developed IVLBL, which demonstrated immunohistochemical positivity for myeloperoxidase. To our knowledge, this represents the first case of a malignant lymphoma to demonstrate such findings.