Astroblastoma: Clinicopathologic features and chromosomal abnormalities defined by comparative genomic hybridization

Astroblastomas are uncommon brain tumors whose classification and histogene sis have been debated. Precise criteria for diagnosis have been described o nly recently, but have not found wide acceptance. We report the clinical, r adiographic, and histopathologic features of 20 astroblastomas, and the chr omosomal alterations in seven cases as detected by comparative genomic hybr idization (CGH). The tumors occurred both in children and young adults (ave rage age, 14 years), most often as well circumscribed, peripheral, cerebral hemispheric masses. Radiographically, the lesions were contrast-enhancing and solid, often with a cystic component. All were characterized histologic ally by astroblastic pseudorosettes, and most displayed prominent perivascu lar hyalinization, regional hyaline changes, and pushing borders in regard to adjacent brain. Tumor cells were strongly immunoreactive for S-100 prote in, GFAP, and vimentin, Staining for EMA was focal. Ten of 20 astroblastoma s were classified as "well differentiated" end 10 were classified as "malig nant,'' largely on the basis of hypercellular zones with increased mitotic indices, vascular proliferation, and necrosis with pseudopalisading. All 10 well differentiated lesions and 8 of 10 malignant lesions were completely resected, None of the well differentiated astroblastomas recurred within th e limited follow-up period. Three malignant astroblastomas recurred, includ ing two incompletely resected tumors, and one that had been totally resecte d. One patient died of disease following recurrence. The most frequent chro mosomal alterations detected by CGH were gains of chromosome arm 20q (4/7 t umors) and chromosome 19 (3/7). The combination of these gains occurred in three, Including two well differentiated and one malignant astroblastoma. O ther alterations noted In two tumors each were losses on 9q, 10, and X,Thes e chromosomal alterations are not typical of ependymoma or infiltrating ast rocytic neoplasms, and suggest that astroblastomas may have a characteristi c cytogenetic profile in addition to their distinctive clinical, radiograph ic, and histopathologic features.