The histogenesis of hemangioblastoma of the brain. A review of twenty-one cases.

Abstract

T UE morphologic and histogenetic criteria distinguishing congenital from neoplastic vascular lesions of the brain have been alternately assailed and upheld. Cushing and BaileS ,s designated hemangioblastomas of the brain as true neoplasms, for they were composed of mature and immature vascular elements which enlarged by proliferation and supposedly contained no glial cells. Thereafter Bailey and Ford 1 demonstrated the presence of astrocytes in such a tumor which infiltrated the cerebellum. Hemangioblastomas of the brain occur most commonly in the cerebellum. 5,15,1s,19,~1 They are usually characterized grossly by a cyst of variable size, filled with clear or xanthochromic fluid, in which a mural nubbin of tumor is found. Microscopically, these mural tumors are composed of variable proportions of adult and immature vascular elements. In some cases the solid mass is composed almost exclusively of adult capillary or cavernous structures and in other instances primarily of vasoformative tissue. In other cysts, careful search is necessary to identify minute buried or sclerosed nodules of tumor. The characteristic cystic development is caused by an inherent line of differentiation of the immature cellular elements of the solid mural nodule. 13 The cyst is the result of the process of differentiation of blood vessels and the formation of primitive plasma from masses of angioblasts. This line of vascular differentiation gives even solid tumors a grossly spongy appearance. When hemangioblastomas of the brain are associated with tumors of the eye, skin, spinal cord or viscera, 2-4, 9-11 the patient may present a distinct clinical syndrome with a familial history. Unfortunately, many clinical variants or anatomical associations of lesions have been dignified by proper names. This cumbersome, although flattering, nomenclature, through sharp selection of cases, tends to obscure the underlying interrelationship of the variants. The occurrence of multiple tumors in a patient with a known hereditary predisposition suggests an arrest or defect in maturation of one or more tissues at a particular time in embryological development. Thus, morphologic variations of vascular tumors may merely reflect a level of maturation of primitive vascular mesenchyme.