Neoplastic angioendotheliomatosis is a rare disorder usually characterized by primarily cutaneous or neurological symptoms. Approximately 40 cases of malignant angioendotheliomatosis with primary central nervous system (CNS) symptoms have been reported. Some investigators have postulated a hematopoietic origin for this neoplasm. Most of the literature, however, has perpetuated the idea that the often bizarre symptoms seen with this entity result from neoplastic endothelial cell proliferation within the small vessels of affected organs, including the brain and spinal cord. This report describes the immunohistochemical examination and confirmation of the cell of origin of this neoplasm based on five previously unpublished cases of malignant angioendotheliomatosis with primarily CNS symptoms. It includes the first documentation of a T-cell lymphoma presenting as malignant angioendotheliomatosis. All cases include autopsy findings, and in four cases the diagnosis was made postmortem. One case was proven by stereotactic biopsy, but the patient succumbed as a result of severe intracranial bleeding that occurred at the time of biopsy. Tissues were studied with avidin-biotin peroxidase immunohistochemical techniques using a panel of monoclonal antibodies directed against the leukocyte common antigen, LN-1, LN-2, and anti-Factor VIII, and also using Ulex europaeus agglutinin 1. Based on the results obtained, the authors conclude that the proliferative cells seen within the vessel lumina are of lymphocytic origin and agree that the condition should more properly be designated intravascular lymphomatosis. The therapeutic implications of this conclusion point to the possible administration of chemotherapy and radiotherapy in an effort to achieve remissions in an otherwise relentlessly progressive neurological disorder.

The histologic staining technique for central nervous system (CNS) tissue known as the Golgi technique was initially developed more than 125 yr ago. It was with this technique that, for the first time, whole nerve cells and their processes were simultaneously observed microscopically. Although the technique was widely used in the early 20th century, its use languished to some extent until the late 1900s when, used in conjunction with ultrastructural studies, it began to provide new insights into microscopic anatomy and pathology of the CNS. Several permutations of the technique have evolved since its early stages. The one represented in this chapter was developed so that Golgi-impregnated CNS tissues could be embedded in polymerized plastic and cut into relatively thick sections for light microscopic study. The advantages are that (a) sections of the clear and almost colorless plastic allow enhanced visualization of the intricate structure and ramification of dendritic elements of CNS neurons, (b) because of the relatively thick microscopic sections (25-30 micro m), details of lengths and arborization of dendritic "trees" can be studied and photographed to provide greater detail than in thinner sections, and (c) numbers and morphologic characteristics of synaptic spines can be precisely evaluated.

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