Capillary Hemangioblastoma

This benign vascular tumor affects adults aged 20 to 50 years. The majority of the tumors are sporadic, few are familial, and about 25% of them are the diagnostic hallmark of the dominantly inherited von Hippel Lindau syndrome. The mutant gene maps to chromosome 3p25-26. The tumor, single or multiple, typically occurs in the cerebellum, seldom in the cerebrum, brainstem, or spinal cord. Extracerebral manifestations are various combinations of retinal angiomatosis, pheochromocy-toma, congenital pancreatic and renal cysts, pancreatic islet cell tumor, renal carcinoma, and cystadenoma of epididymis. An erythropoietin hormone produced by the cells of capillary hemangioblastoma causes secondary polycythemia.

Clinically, it presents with slowly progressive cerebellar symptoms and raised ICP. Visual impairment from a retinal hemangioma may either precede or follow the cerebral symptoms.

Grossly, the tumor is a reddish mural nodule in the wall of a large cyst, which contains xanthochromic fluid (Fig. 11.42). Histologically, hemangioblastoma has two components: a capillary network lined with endothelial cells and large foamy stromal cells. These cells immu-

figure 1 1.42

Capillary hemangioblastoma. A. Macrosection of the cerebellar hemisphere shows a large cyst with a small tumorous mural nodule. B. The tumor consists of endothelial cells lining capillary channels and (C.) large foamy stromal cells that contain lipid (HE).

figure 1 1.42

Capillary hemangioblastoma. A. Macrosection of the cerebellar hemisphere shows a large cyst with a small tumorous mural nodule. B. The tumor consists of endothelial cells lining capillary channels and (C.) large foamy stromal cells that contain lipid (HE).

noreact for vimentin and may contain lipid droplets (see Fig. 11.42).

Hemangiopericytoma

This malignant tumor of adults is described in the section, Tumors of the Meninges.

Anagiosarcoma

This malignant tumor of the brain and meninges consists of vascular channels lined with atypical endothelial cells displaying frequent mitoses.

Malformative Vascular Lesions

These circumscribed mass lesions of vascular channels are characterized by:

• An absence of proliferative tendencies; they may, however, expand by dilatation of vascular channels

• Single or multiple presentation

• Sporadic or familial occurrence

Clinically, vascular malformations usually manifest in adults and present with seizures and headaches. Progressive or fluctuating neurologic deficits follow. Serious complications are recurrent parenchymal and subarach-noid hemorrhages.

Cavernous angioma is a group of sinusoidal collagenous vascular channels separated by gliotic tissue. It is preferentially situated in the cerebral hemispheres and pons (Fig. 11.43).

The arteriovenous angioma is a conglomeration of arteries and veins of various sizes commonly situated in the cerebral hemispheres, often in the distribution of the middle cerebral artery. The vascular walls degenerate and proliferate, leading to luminal stenosis and throm-botic occlusion. The intervening neural tissue undergoes ischemic necrosis and eventually becomes gliotic. Distant ischemia develops from the "stealing" of blood from neighboring tissue (see Fig. 11.43).

The venous angioma consists of clusters of tortuous veins separated by gliotic tissue.

Capillary telangiectases consist of a group of dilated, varicose capillaries separated by normal tissue. Found in the pons, medulla, and cerebral white matter, they may produce slowly progressing neurologic deficits. Often they are incidental findings at autopsy (see Fig. 11.43).

LYMPHOMAS AND HEMATOPOIETIC TUMORS

This group encompasses the malignant primary lymphomas of the CNS and tumors derived from neoplastic plasma cells and histiocytes.

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trr figure 1 1.43

Vascular malformations. A. Cavernous angioma (van Gieson). B. Arteriovenous malformation. Hemosideum pigments are scattered around the lesion. C. Capillary telangiectasis (HE).

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