Vascular and Hematopoietic Neoplasms

CHAPTER 31 Vascular and Hematopoietic Neoplasms



The focus of this chapter is on tumors that are vascular or of blood cell origin. These include hemangioblastoma, hemangiopericytoma, primary central nervous system (CNS) lymphoma, intravascular lymphoma, leukemia, and plasmacytoma. These neoplasms combined make up fewer than 10% of CNS tumors.



HEMANGIOBLASTOMA


Hemangioblastoma is a benign vascular tumor composed of endothelial and stromal cell components that can occur throughout the neural axis. The majority of these tumors are sporadic (75%), with the remaining associated with von Hippel-Lindau (VHL) disease.1 It is also referred to as capillary hemangioblastoma and is the most common primary intraparenchymal tumor to occur in the posterior fossa in adults.







Imaging






HEMANGIOPERICYTOMA


Hemangiopericytoma is a malignant tumor originating from the pericytes of Zimmerman around capillaries and postcapillary venules. The intracranial tumor arises from meningeal capillary pericytes and is also called an angioblastic meningioma. This tumor is also found in the skin and the musculoskeletal system.12







Imaging


Hemangiopericytoma can be indistinguishable from meningioma on imaging.






PRIMARY CNS LYMPHOMA


Primary CNS lymphoma is an extranodal non-Hodgkin’s lymphoma (NHL), usually a diffuse large B-cell lymphoma that affects the CNS. The majority of CNS lymphomas are primary lesions (93%). The remaining are secondary lymphomas metastatic to the CNS.






Pathology


Most lesions are supratentorial (75%) and have a predilection for the cerebral hemispheres, followed by basal ganglia, corpus callosum, and cerebellum. Leptomeningeal involvement occurs in about 12% of cases. Dural involvement is rare in primary CNS lymphoma. One percent of tumors occur in the spinal cord.23,24,27


Primary CNS lymphoma is frequently surrounded by edema, commonly spreads to leptomeninges and subpial regions, and is multifocal in almost 50% of cases. Focal necrosis and hemorrhage are common.25


Histology demonstrates monotonous, closely packed blue cells with a high degree of cellularity. Infiltrates are seen far beyond the borders of the grossly observed mass. Necrosis and hemorrhage are much more frequent in the lesions of immunocompromised patients.26


Neoplastic cells tend to cluster along vascular channels, a phenomenon that supports the theory that CNS lymphoma spreads diffusely through the brain by way of the perivascular spaces.26 A vasculitis-like appearance on histopathology may be seen because of tumor infiltrating the blood vessel walls. This angiocentric growth pattern—tumor cells forming multiple, thick layers around the host vessels and widening of the perivascular space—is one of the histopathologic hallmarks of the disease.


Immunohistologic analysis is essential to the diagnosis. Antibodies are directed at common leukocyte antigens, pan-B antigens, and pan-T antigens. Tumors typically contain a population of atypical pleomorphic B cells mixed with reactive T cells. Even though primary CNS lymphoma is considered monoclonal, the lesion virtually always contains at least two cell populations, one of which is neoplastic and the other one reactive.


In general, lymphomas are divided into low-grade, highgrade, and possibly intermediate-grade NHL. No intermediate-grade cases have been reported since 1983. Today almost half of CNS lymphomas are of the high-grade, large-cell, immunoblastic subtype.24


The CSF may show elevated protein and decreased glucose levels. Cytology will often be negative.



Imaging



Jan 22, 2016 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Vascular and Hematopoietic Neoplasms
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