Glioblastoma

GlioblastomaMorphologic and Molecular Genetic Diversity C. Ryan Miller, MD, PhD; Arie Perry, MD ● Context.—Glioblastoma (GBM), the most common primary intracranial malignancy, is a morphologically diverse neoplasm with dismal prognosis despite multimodality therapy. Only 3 distinct morphologic variants of GBM are currently recognized by the current World Health Organization classification scheme, including GBM, giant cell GBM, and gliosarcoma. Additional variants, some of which have significant morphologic overlap with tumors that have more favorable prognosis and treatment response rates, particularly anaplastic oligodendroglioma, have been described since its publication in 2000 and may be included in the next classification. iffuse, infiltrative gliomas are the most common primary intracranial neoplasms, accounting for 40% of all primary and 78% of all malignant central nervous system tumors.1 More than 80% of these tumors are considered high-grade (grades III and IV) when diagnosed according to the current World Health Organization (WHO) classification, a system based on morphologic evidence of differentiation along astrocytic, oligodendroglial, or mixed lineages. Classification and grading criteria for astrocytic neoplasms are well established, having been refined periodically during the last 80 years from the classification schemes of Bailey and Cushing,2 Kernohan,3 Ringertz,4 Nelson,5 St. Anne-Mayo,6,7 and WHO.8,9 The WHO 2000 criteria are currently the most widely accepted scheme and are based largely on the St. AnneMayo classification. For example, it uses mitotic activity to distinguish anaplastic astrocytoma (AA), WHO grade III, from its low-grade counterpart, diffuse astrocytoma, WHO grade II. Median overall survival (OS) for patients with AA is typically 3 to 5 years.10 Microvascular proliferation (MVP), loosely defined to include endothelial hypertrophy, endothelial hyperplasia, and glomeruloid vessels, and/or necrosis are distinguishing features of WHO grade IV astrocytoma, the latter being synonymous with the commonly used term glioblastoma multiforme or simply glioblastoma (GBM) in the current WHO scheme.10 Despite Accepted for publication October 25, 2006. From the Division of Neuropathology, Washington University School of Medicine, St Louis, Mo. The authors have no relevant financial interest in the products or companies described in this article. Reprints: Arie Perry, MD, Division of Neuropathology, Department of Pathology and Immunology, Washington University School of Medicine, 660 S Euclid, Campus Box 8118, St Louis, MO 63110 (e-mail: [email protected]). Arch Pathol Lab Med—Vol 131, March 2007 Objective.—To summarize the morphologic and molecular genetic diversity of both well-established and novel GBM variants and outline our approach to these heterogeneous neoplasms and their distinction from other diffuse, high-grade gliomas. Data Sources.—Published literature and our own experience in an active academic diagnostic surgical neuropathology practice were reviewed. Conclusions.—Precise subclassification of GBM is required for accurate prognostication and appropriate treatment planning. (Arch Pathol Lab Med. 2007;131:397–406) advances in microsurgical techniques, radiation, and chemotherapy, GBM is still associated with a median OS of approximately 1 year.6 In its most mature and prognostically significant manifestation, MVP is recognized as multilayered tufts of hyperplastic and mitotically active endothelial cells, accompanied by smooth muscle cells and pericytes. The presence of MVP in GBM has been correlated with hypoxia-induced neoangiogenic and infiltrative phenotypes, the former of which is characterized by expression of cytokines such as vascular endothelial growth factor.11,12 Microvascular proliferation is both temporally and spatially linked to the presence of necrosis, particularly pseudopalisading necrosis.11,12 These morphologic criteria are highly reproducible and serve as useful prognostic factors for OS.13–15 Glioblastoma may arise through 2 distinct pathways of neoplastic progression. Tumors that progress from lowergrade (II or III) astrocytic tumors, termed secondary or type 1 GBMs, typically display both well-differentiated and poorly differentiated foci. Secondary GBMs develop in younger patients (fifth to sixth decade), with time to progression from lower-grade lesions ranging from months to decades. In contrast, primary, type 2 GBMs develop in older individuals (sixth to seventh decade), have short clinical histories (less than 3 months), and arise de novo without any evidence of a lower-grade precursor. Primary and secondary GBMs also harbor distinct molecular genetic abnormalities: Primary GBMs are characterized by relatively high frequencies of EGFR amplification, PTEN deletion, and CDKN2A (p16) loss, whereas secondary GBMs often contain TP53 mutations, especially those involving codons 248 and 273 or G:C→A:T mutations at CpG sites.16 The clinicopathologic and molecular genetic features of primary and secondary GBM have been recently reviewed in detail by Ohgaki and colleagues.16 GBM Variants—Miller & Perry 397 D . deletion. absent. to .. Gemistocytes were first described by Franz Nissl as glia (gemaestete glia) with voluminous cytoplasm.. hyperchromatic nuclei.. In this context... ....... . / / PVI . In addition. . This work and its historical underpinnings has been summarized in a recent review by Tihan and colleagues.. / / / / / Mucin-filled microcysts . Nevertheless. .. Such tumors may also harbor mucin-rich microcystic spaces.26 Granular cell astrocytomas are rare astrocytic neoplasms composed of sheets of large... the WHO defines a gemistocytic astrocytoma as an astrocytoma composed of more than 20% gemistocytes. ...... GBMs comprise a morphologically highly heterogeneous neoplasm. ..27 Some groups have suggested that these tumors behave more aggressively than their non-gemistocytic grade II counterparts and thus deserve a grade III designation.22 The prognostic impact of gemistocytic cytology in astrocytomas has been an active area of investigation during the last 40 years. gliosarcoma. the cellular composition is heterogeneous and may include fibrillary.. PVI. . Gemistocytic astrocytoma (WHO grade II) with greater than 5% gemistocytes have been reported to progress more rapidly to GBM. .. . gemistocytic astrocytoma is currently recognized as a distinct variant only of diffuse astrocytoma (WHO grade II). . hyperchromatic nuclei. / Nuclear irregularity ... .. irregularly shaped.. even within a single tumor... amplification. .. % 70 4 . * Fib indicates fibrillary. % 28 65 .. gemistocytic.. round uniform cells with sharp nuclear membranes and bland chromatin) before one invokes an oligodendroglial component in the diagnosis. Although gemistocytes may be found in all grades of astrocytoma (II. 89 27 EGFR amp/10q del. elongated to irregularly shaped.. / .... other variants of GBM with distinct clinicopathologic and genetic features have been described (Table 1).. . Cytoplasmic granules . . VARIANTS OF GBM The term GBM was coined by Mallory in 191417 and solidified in the lexicon of surgical neuropathology by Bailey and Cushing in 1926. eccentric.... raising the differential diagnosis of high-grade oligodendroglial (HGO) neoplasms (WHO grade III anaplastic oligodendroglioma [AO... and short cytoplasmic processes (Figure 2.Table 1... GCA. .. Multinucleated cells . ..18 Three GBM variants are recognized as distinct clinicopathologic entities in the current WHO classification: conventional GBM. . Conventional GBM Even within the conventional GBM category. .. Perivascular lymphocytic infiltrates are also a common but nonspecific finding in these tumors (Figure 2. Neoplastic fibrillary astrocytes contain enlarged.. increasing frequency.2 As the original designation multiforme implies. ..... Because of cross sectioning of spindled or cylindrical nuclei. GBM with oligodendroglial features.. PTEN mut.. a significant fraction of cells should have classic cytology (eg.. % . . gemistocytic.. infrequent.28–31 Most granular cell astrocytomas are GFAP positive and may nonspecifically display GBM Variants—Miller & Perry . and gliosarcoma (GS). . . / 1p del.. the cellular composition. perivascular inflammation. %43 32 4 .10. ... eosinophilic GFAPimmunoreactive cytoplasm. giant cell GBM (GC-GBM). codeletion. . 5 .. ... . 6 43 1p/19q codel.... .... % 36 8 . .. and mut. . . . and variable glial fibrillary acidic protein (GFAP)– immunoreactive processes that form a loose. 0 37 .... 0 22 EGFR amp... and IV).... giant cell. . .. and sought to correlate its significance with patient outcomes.. ...22–26 Various reports have quantified the percentage of gemistocytes present in a tumor. deceptively bland cells with abundant granular..... . % ··· . 89 23 . GBM-O. ... no data available.. O3] and WHO grade III anaplastic mixed oligoastrocytoma [AOA... . Sources of molecular genetic frequencies are referenced by column except PTEN mutation (row). small cell astrocytoma. fibrillary matrix (Figure 1).. Once thought to represent a reactive component. periodic acid-Schiff–positive cytoplasm (Figure 3).. 3 24 19q del.19 Gemisto398 Arch Pathol Lab Med—Vol 131. MOA3]). mutation.... therefore.. GS. a feature termed the gemistocytic index. . the prognostic significance of the gemistocytic index in grade II and III astrocytomas still remains unclear and no studies have examined the independent significance of this factor in tumors with the grade IV features of MVP and/or necrosis... codel. % . . we discuss the cytologic heterogeneity that may be encountered in the variants of GBM and outline our approach to their subclassification... and/or occasional giant cells (GCs). scant cytoplasm.. % ... . these cells have been found to harbor TP53 mutations20 and cytogenetic abnormalities (chromosome 7p gains and 10q losses)21.. In the present review. glassy. % 31 19 .. III. SCA.. March 2007 cytic astrocytes contain plump. However. . / / Perinuclear haloes ... granular cell astrocytoma. . amp.... they are now thought to represent a true neoplastic component.. neoplastic fibrillary astrocytes may also appear to have occasional rounded nuclear profiles. / / / / / / Reticulin meshwork . 5 4 63 7 9p (CDKN2A) del..... 10q (PTEN ) del.... A and B). Feature Clinicopathologic and Molecular Genetic Features of Glioblastoma Multiforme (GBM) Variants* Tumor Primary16 Secondary16 Fib Gem GCA GC32 GS43 SCA57 GBM-O57 Peak age (decade) 6–7 5–6 6–7 6–7 6–7 5–6 6–7 6–7 5–6 Circumscription ... ... del..10.. . ... A). In other words. 27 38 . . 56 4 TP53 mut.. can vary widely and mixed histologic features are typical.. GC.. Gem. . . A.3 months for non–GC-GBM. high-frequency loss of heterozygosity at 9p. Median OS was 11. often appearing multinucleated (Figure 4. GCGBMs contain clinical and molecular genetic features of both primary and secondary GBMs and as such occupy an intermediate position between these two.Figure 1. 7 grade III. Figure 2.32. and 11 grade IV tumors) and found that these tumors were more aggressive than non-granular cell astrocytomas of the same grade. Giant Cell GBM Giant cell GBM constitutes approximately 5% of GBMs and is recognized as a distinct clinicopathologic entity in the WHO 2000 classification.28.29 Brat and colleagues28 reported the largest series of such tumors to date (22 cases. the prognosis remains poor overall. cigar-shaped or irregularly shaped. As the name implies. eccentric.48) after adjusting for patient age and surgery type (resection vs stereotactic needle biopsy).36 The process of endoreduplication results in multiple cycles of DNA replication associated with a failure of cell division.10. Figure 4. This tumor also harbors pseudopalisading necrosis with peripheral palisading of tumor cells around a central core of necrosis (hematoxylin-eosin. Giant cell glioblastoma multiforme.10 Although occasional neoplastic GCs may be found in conventional GBM. hyperchromatic nuclei and scant cytoplasm.33 Several reports have demonstrated a slightly better prognosis for GC-GBM than for conventional GBM. GBM Variants—Miller & Perry 399 .10. Gemistocytic glioblastoma multiforme. Among 453 supratentorial GBMs newly diagnosed between 1990 and 2005. Perivascular inflammatory infiltrates are particularly common in these tumors (hematoxylin-eosin. Their molecular genetic features include relatively high frequencies of Arch Pathol Lab Med—Vol 131. and 17p. Given their average survival of 7. A.29 Similar to astrocytomas with nongranular cytology. often bizarre. Tumor cells contain enlarged. However. protein kinase C. A).6 months. and 19p13. Figure 3. March 2007 TP53 mutations (75%–90%) and PTEN deletion (5%–30%). Neoplastic gemistocytes contain plump. Granular cell glioblastoma multiforme. B). Fluorescence in situ hybridization analysis shows marked gains of chromosome 19 (19q13.28. original magnification 200). therefore. eosinophilic cytoplasm. evident as either dense or multivesicular bodies. Using antibodies to specific phosphorylation sites on vimentin and GFAP catalyzed by various kinases. hyperchromatic nuclei with occasional small nucleoli. These patients were approximately 10 years younger than those with non–GCGBMs. only 7 (1. fibrillary background. these tumors may also harbor TP53 mutations. Rho. this has similarly been our experience at Washington University School of Medicine. This tumor is composed of markedly enlarged neoplastic astrocytes with multiple. cytoplasmic epithelial membrane antigen but no cytokeratin immunoreactivity. it may indeed be appropriate to consider them variants of GBM. including 4 grade II. compared with 9.35. these cells are a dominant cytologic component in GC-GBM. including cdc2. hyperchromatic nuclei (hematoxylin-eosin. red) in 2 apparent giant cells within this field. this difference was not statistically significant (log-rank P . glassy. original magnification 400). and indistinct processes that form a dense.34 Nevertheless. green. whereas EGFR amplification and CDKN2A deletion are rare in comparison to conventional GBMs. the tumor cells are markedly enlarged and bizarre. A potential molecular mechanism for GC formation has recently been described. consistent with polyploidy (original magnification 1000). CF. and less frequent loss of heterozygosity at 1p and 19q.4 months for GC-GBM. original magnifications 400 [A] and 200 [B]). other chromosomes were similarly gained.30 Ultrastructural studies have shown that the cytoplasmic granularity correlates with increased lysosomes. Fibrillary glioblastoma multiforme. Giant cell GBMs are typically well-circumscribed masses that occur in younger patients (fifth decade). These tumor cells are occasionally mistaken for macrophages (hematoxylin-eosin. original magnification 200). irregularly shaped.5%) were GC-GBMs. As shown in Table 2. 10q. thus causing markedly enlarged polyploid nuclei with extensive chromosomal gains (Figure 4. These tumors are composed of sheets of large cells with bland oval nuclei and abundant granular cytoplasm. B. B. . These components are often intermingled (hematoxylin-eosin. D.4 . Prognostic Impact of Morphologic Variants in 453 Newly Diagnosed. 400 Arch Pathol Lab Med—Vol 131. epithelial metaplasia may also occur in either GS or conventional GBM. gene deletion. The mesenchymal component may also show a wide variety of morphologic appearances. A.Table 2. aurora-B kinase has been shown to be overexpressed in astrocytomas in general. Such cases often invoke a differential diagnosis of metastatic carcinoma.3 11. The latter is illustrated in Figure 6.10 These tumors are characterized by their well-circumscribed. D). investigators have shown that the molecular alteration that causes failure of cytoplasmic cleavage in cultured multinucleated GCs is loss of aurora-B kinase function. B. Adult ( 20 y) Supratentorial Glioblastoma Multiformes (GBMs) at Washington University School of Medicine (1990–2005)* Tumor Characteristic GBM GC-GBM GS SC-GBM GBM-O n 388 7 % 85. small cell GBM. 10 21 27 2. In addition to sarcomatous differentiation. with both mRNA and protein levels correlating with WHO grade.6 52.2 4. and adipose lines.10 These areas are generally characterized by dense extracellular matrix deposition. no data available.6 6. These tumors show a well-circumscribed. E and F. whereas the sarcomatous component is reticulin rich (top and bottom) (original magnification 100). lower).36 Importantly. original magnification 100).6 47. the molecular basis for aurora-B kinase dysfunction (mutation. C. such as cartilaginous differentiation (hematoxylin-eosin. an ‘‘adenoid glioma’’ that was immunoreactive for both GFAP (Figure 6. and .5 Mean age. osseous. gliosarcoma. with evidence of differentiation along fibroblastic. . original magnifications 400 [E] and 200 [F]). with oligodendroglial features.35 However. GC-GBM indicates giant cell GBM. The glial element expresses glial fibrillary acidic protein (immunoperoxidase. mo 9.33 . smooth and striated muscle. The sarcomatous component may also show evidence of other mesenchymal elements. E and F).1 57..3 27. March 2007 GBM Variants—Miller & Perry . C. Gliosarcoma. Gliosarcoma and ‘‘Adenoid’’ GBM Gliosarcoma constitutes approximately 2% of GBMs and is likewise recognized as a distinct clinicopathologic entity in the WHO 2000 classification. GBM and aurora-B. The glial component of GS may show any of the aforementioned cytologic features and is typically immunoreactive for GFAP (Figure 5.6 14.4 Log-rank P (vs GBM) .0 59. B) and low-molecular-weight cytokeratins (CK7. including areas of keratinizing squamous or glandular differentiation. C. A and B). loss of aurora-B kinase–mediated phosphorylation was confirmed in human GC-GBM samples. original magnification 100). nonglial components (left) (hematoxylin-eosin. upper) and contrasting with the typically reticulin-poor glial component (Figure 5. % 64 57 Median OS. original magnification 200). A. methylation) in GCs and its overexpression in non-GC-GBM remains to be established.37 Therefore. . y 61. A reticulin stain is helpful in identifying the 2 distinct components: The glial component is reticulin poor (center).. biphasic growth pattern with clearly identifiable glial (right) and metaplastic. Figure 5.48 * P adjusted for patient age and surgery type. SC-GBM. GBM-O. biphasic growth pattern with clearly identifiable glial and meta- plastic mesenchymal components (Figure 5.1 Resection. the latter evident on reticulin-stained sections (Figure 5.9 90 91 93 7.95 .35.7 1.01 GS.. cartilaginous (Figure 5. 47 OTHER VARIANTS OF GBM Additional variants of GBM have been described beyond those published in the 2000 WHO classification scheme. This difference was not statistically significant (log-rank P .50 although its prognostic utility remains less well defined for these neoplasms.38 However.43 The notion that the sarcomatous element represents mesenchymal metaplasia analogous to that seen in carcinosarcomas elsewhere in the body comes from data demonstrating the presence of 1 or more identical genetic aberrations in both elements from individual tumors. Adenoid glioblastoma multiforme. In this regard. Overall. glioblastoma with oligodendroglial features (GBM-O). which was immunoreactive for a variety of cytokeratins. compared with 9. and its association with responsiveness to adjuvant therapy and improved prognosis. This too has been our experience at Washington University School of Medicine (Table 2). immunoperoxidase.48–51 Codeletion of 1p/19q has been shown to occur most frequently (50%–80%) in morphologically classical AO. Median OS was 7. specifically codeletion of material on chromosomes 1p and 19q. Arch Pathol Lab Med—Vol 131. adult supratentorial GBMs. These patients were of similar age to those with no sarcomatous component.3 months for conventional GBM.53 A subset ( 20%) of AOA also harbor 1p/19q codeletion. Among the 453 newly diagnosed.52. These include small cell astrocytomas (SCAs). identical genetic alterations have been described in microdissected portions from the glial and epithelial elements of adenoid GBMs and GSs.10. Regardless. these variants have significant morphologic overlap with other recognized clinicopathologic entities. particularly HGO neoplasms. all of which pose little diagnostic difficulty for the experienced neuropathologist on routine histopathologic examination.33) after adjusting for patient age and surgery type. Identification of signature molecular genetic alterations. has made accurate histopathologic and molecular genetic characterization of these neoplasms of paramount importance for proper treatment planning and precise prognostication. In contrast to granular cell astrocytoma. only 10 (2. Several reports have demonstrated a slightly better prognosis for GS than for conventional GBM. The existence of epithelial-mesenchymal transition is an area of intense debate within the cancer research community and has been extensively reviewed elsewhere. March 2007 .10. suggesting that this too represents metaplasia. GC-GBM. including CK7 (C) (hematoxylin-eosin. original magnification 200 [A]. the latter supports a monoclonal process rather than a collision tumor.2%) were GSs. these tumors are exceedingly rare and are thus far not recognized as a distinct clinicopathologic entity by the WHO.the differences in OS have been statistically insignificant in most series. and CDKN2A deletions. Even when histopathologic GBM Variants—Miller & Perry 401 Figure 6. it is clear that the metaplastic component in GS is neoplastic and frequently harbors cytogenetic and molecular abnormalities similar to those found in the glial component. The glial component (B) is intermingled with the epithelial component. original magnifications 200 [B] and 400 [C]). and GBM with primitive neuronal (primitive neuroectodermal tumor [PNET]–like) features. a phenomenon postulated to be essential for systemic metastasis in non–central nervous system epithelial tumors.46. Extensive work in developmental and tumor molecular cell biology has elucidated potential molecular mechanisms responsible for epithelial-mesenchymal transition.39–42 The possibility of an analogous role of epithelial-mesenchymal transition in GS is currently unexplored. This tumor is an extremely rare variant with epithelial (glandular) metaplasia (A). C). Metaplasia in non–central nervous system epithelial tumors is not infrequently encountered in general surgical pathology. Figure 6. and GS. GSs are genetically similar to primary GBMs: 20% to 40% of tumors harbor TP53 mutations.43–45 Similarly.6 months for GS. The only exception to this generalization is the relative infrequency of EGFR amplification in these tumors. PTEN deletions. Immunohistochemical studies are a useful adjunct in diagnosing SCA: Tumor cells typically contain long. including perineuronal satellitosis (Figure 7. C. The tumor vasculature is sometimes composed of a delicate. Morphologic features of small cell astrocytoma. A) and a markedly elevated MIB-1 (Ki-67) labeling index (Figure 8. and D]). D). Delicate chicken-wire capillary vasculature is common (D) (hematoxylin-eosin. in which median OS ranges from 5 to 10 years. SCA can show cortical infiltration and secondary structuring. adult supratentorial GBMs) at Washington University School of Medicine is listed in Table 2. with frequencies even higher than conventional GBMs (Table 1). A and B).95) from that of conventional GBM after adjusting for patient age and surgery type. In contrast to AO. SCAs show chromosome EGFR amplification and chromosome 10q (PTEN) deletion. Combined EGFR amplification and 10q deletion is likewise more prevalent in SCA compared with conventional GBM. classification is refined by ancillary molecular genetic analyses. the clinical behavior of SCA is much more aggressive.3 months and was not statistically significantly different (log-rank P . GFAP-positive cytoplasmic processes (Figure 8. SCAs rarely harbor deletion of either 1p or 19q and we have never encountered codeletion of these chromosomes (Table 1). uniformly oval nuclei with mild hyperchromasia and minimal discernible cytoplasm. chicken-wire capillary network (Figure 7.54 Small Cell Astrocytoma Small cell astrocytoma is a variant of GBM with considerable morphologic overlap with AO on routine hematoxylin-eosin–stained sections. C).56 It is for this reason that accurate diagnosis of SCA is imperative for accurate prognostication and proper treatment planning. Like other diffuse gliomas. diagnostic discrepancies remain frequent for the HGO neoplasms. 402 Arch Pathol Lab Med—Vol 131.55.13–15.55. March 2007 In contrast to AO.6% of 453 newly diagnosed. thin. Their median OS was 14. with median OS virtually indistinguishable from conventional GBM. even among experienced neuropathologists. It is composed of a large ( 80%) monotonous collection of astrocytes with small. Rather. These patients were of similar age to those with conventional GBMs. original magnifications 400 [A] and 200 [B.56 The histopathologic hallmarks of this tumor are its bland nuclear cytology and striking mitotic activity (Figure 7.11. We have recently GBM Variants—Miller & Perry . B). Identification of characteristic molecular genetic alterations in SCA has provided an additional diagnostic aid in challenging cases.Figure 7. Our experience with 21 SCAs (4. These tumors are composed of a monotonous population of cytologically bland cells with uniform oval nuclei with minimal hyperchromasia and minimal discernible cytoplasm (A and B) and may show secondary structuring such as perineuronal satellitosis (C). respectively. Mitotic activity and MIB-1 (Ki-67) labeling index is markedly elevated (immunoperoxidase. We considered the diagnosis of an AOA only if distinct astrocytic (Figure 9. and AOAs) analyzed by fluorescence in situ hybridization (FISH) for EGFR amplification. C and D. adult supratentorial HGGs specifically to address this issue. including AAs. 10q deletion was slightly more sensitive (90%) but slightly less specific (64%) for the diagnosis of SCA (Figure 8. original magnification 400). 13 GSs. D). The 2 forms of HGO neoplasms. AO and AOA. 581 GBMs (including 120 SCAs. by the presence of any one or more of the following histologic features: brisk mitotic activity. highgrade gliomas (HGGs. Tumor cells typically contain long. are distinguished from their lowgrade counterparts. the sensitivity and specificity of 10q deletion for the diagnosis of GBM were 81% and 71%. microvascular proliferation. 215 AOAs. GBM Variants—Miller & Perry 403 . respectively (original magnifications 400 [C] and 1000 [D]). what diagnostic features constitute such entities? We recently performed a retrospective analysis of prognostic factors in 1093 newly diagnosed. No significant weight is given to any of these features. B. A. Immunohistochemical and genetic features of small cell astrocytoma. if so.57 This study included 81 AAs. Arch Pathol Lab Med—Vol 131. and 216 AOs diagnosed according to current WHO 2000 criteria. Because these molecular genetic abnormalities may occasionally be found in other HGGs. AOs. oligodendroglioma and oligoastrocytoma. Among 222 HGGs with 106 SCAs that were analyzed for 10q abnormalities by FISH. thin glial fibrillary acidic protein–positive cytoplasmic processes (immunoperoxidase. C).57 Among 239 diffuse. GBMs. and necrosis. March 2007 GBM With Oligodendroglial Features The current WHO classification of HGO neoplasms contains significant ambiguities. FISH analysis does not serve as a replacement for routine histopathologic examination but only as an objective adjunct to confirm the initial morphologic impression of SCA or GBM in general.Figure 8. the sensitivity and specificity for the diagnosis of GBM were 54% and 94%. Fluorescence in situ hybridization analyses for chromosomes 7 (EGFR region in red. original magnification 200). EGFR amplification was equally sensitive (92%) and slightly more specific (64%) for SCA (Figure 8. respectively. which has given rise to the following debate within the neuro-oncology community: Do grade IV variants of HGO neoplasms exist and. including 108 SCAs. single red and green signals). analyzed the diagnostic utility of molecular genetic analysis in the diagnosis of SCA. and 2 GC-GBMs). centromere for chromosome 7 in green) and 10q (PTEN in green and DMBT1 in red) typically reveal evidence of EGFR gene amplification (C) and 10q deletion (D. 5–3. Some of the variants described in this article have recently been added to the upcoming WHO 2007 scheme as distinctive ‘‘patterns’’ of GBM. too few cases have been reported to determine the behavior or optimal therapy. B) components were evident. March 2007 . approximately 10 to 15 years younger than conventional GBM. Their median OS was 27. as several of the newly defined variants described since the publication of the WHO classification in 2000 have significant morphologic overlap with tumors that have more favorable prognosis and treatment response rates. Necrosis. We found that the presence of any type of necrosis (Figure 9. remarkably high mitotic and Ki-67 indices (close to 100% in some. CONCLUSION Glioblastoma multiformes are morphologically diverse neoplasms with poor prognosis. Survival data for a subset of these GBM-O cases seen at Washington University School of Medicine is presented in Table 2. the majority of our cases have occurred in adults and had foci resembling conventional GBM. Thus. neurofilament protein. GBM With Primitive Neuronal (PNET-like) Features Rare examples of high-grade glioneuronal tumors or GBMs combined with cerebral neuroblastoma/supratentorial PNET have been previously published but remain relatively poorly characterized. but its infrequent occurrence in these tumors precludes reliance on this feature in establishing the diagnosis. Among 586 diffuse HGGs analyzed by FISH for 1p/19q abnormalities. Glioblastoma multiforme with oligodendroglial features (GBM-O or mixed oligoastrocytoma. with either geographically distinct (A) or intermingled (not shown) components. compared with 86.4. these tumors more frequently show solitary 19q deletion (21% of 58 analyzed tumors). A). D). patient age was similar to that seen in GC-GBM. respectively. More widespread application of the principles described in this review may permit more accurate prognostication and appropriate treatment planning in the future.8 months. Precise subclassification is becoming increasingly important. Figure 10. the presence of solitary 19q deletion may be a useful molecular genetic feature to confirm the impression of a GBM-O after routine histopathologic examination. grade IV).01). grade IV (MOA4). In contrast to the finding of codeletions in roughly 85% of our AOs. Cox P . these frequencies are nearly identical to those we have encountered in mixed oligoastrocytomas overall. Nonetheless.We therefore consider WHO grade III AOA with necrosis to constitute a distinct grade IV variant of AOA and routinely designate such neoplasms as GBM-O. No significant effect of necrosis on median OS (89. neuron-specific enolase).9 months for those without necrosis (log-rank P . often as consults with the differential diagnosis including an unusual GBM versus a supratentorial PNET with extensive glial differentiation (Figure 10.32). or combined 1p/19q (22%) is relatively infrequent in GBM-O (Table 1). Interestingly. in line with the relatively better prognosis for oligodendroglial neoplasms in general. A) in an otherwise grade III AOA was a strong predictor of poor survival independent of patient age (hazard ratio 2. the sensitivity and specificity of solitary 19q deletion for the diagnosis of AOA and GBM-O were 25% and 93%. A) and oligodendroglial (Figure 9. In support of the former interpretation. An alternative.8 months) was evident in patients with pure AO (log-rank P . Neu-N.001): median OS for AOA patients whose tumors featured necrosis was 22. we have encountered a number of such cases. GBM Variants—Miller & Perry Figure 9. particularly pseudopalisading necrosis (A). significantly longer than that for conventional GBM after correction for patient age and surgery type (P . and convincing evidence of neuronal or neuroblastic differentiation.001). Moreover. B) and expression of neuronal antigens (eg. original magnifications 100 [A] and 200 [B]).8 months) than to AOA without necrosis. distinguishes these tumors from their grade III counterparts (AOA) (hematoxylineosin. the median OS of AOA with necrosis was closer to GBM (9. markedly hyperchromatic cells. synaptophysin [Figure 10. analogous to GBM in general. 404 Arch Pathol Lab Med—Vol 131. either as geographically separated (Figure 9) or intermingled (not shown) areas. To date.58 Similarly.4 months. 19q (43%). C]. high nuclear-cytoplasmic ratios. The primitive neuronal (PNET-like) element often looks like a separate clone with nodules of markedly increased cellularity. such as Homer-Wright rosettes (Figure 10. equally valid designation would be highly anaplastic oligoastrocytoma. although most of the patients we have encountered have died in less than a year. sometimes with foci of low-grade glioma in either the same or a prior biopsy. In this cohort of 27 patients (6% of 453 GBMs seen between 1990 and 2005). 95% confidence interval 1. GBM-O show evidence of both astrocytic (A) and oligodendroglial (B) differentiation. deletion of either 1p (24%). These tumors portend a significantly better prognosis than other variants of GBM.7. Dessen P. Cavenee WK. 15. Nissl F. 2nd ed. Cancer. Philadelphia. 1949. France: IARC Press. Nelson DF. Reis RM. Ohgaki H. 2000. 1991. Grading of gliomas. Germany: Springer-Verlag.3:99–103. 2000.79:1381–1393. Davis RL. Simmons ML. Glioblastoma multiforme with neuronal peripheral neuroectodermal tumor–like features. et al. 6. Improving diagnostic accuracy and interobserver concordance in the classification and grading of primary gliomas. Md (grant T32CA009547 to C. Bethesda. Hara A. References 1. Supported in part by a cancer biology training grant from the National Cancer Institute. 7. Kleihues P. 2. Coons SW. Jourde B. World Health Organization Classification of Tumours. Scheithauer B. 1950. 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