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Mixed Gliomas

Synonyms: Oligoastrocytoma

Definition

Diffusely infiltrative glial tumor with divergent forms of glial differentiation, most commonly astrocytic and oligodendroglial components.

Clinical Features

Diagnosis

Oligoastrocytoma

  • One of the least reproducible diagnoses in surgical neuropathology
  • Not a homogeneous biologic entity
  • Oligodendrogliomas composed in part of GFAP-positive ‘minigemistocytic’ elements retaining the oligodendrocyte's rounded nuclear profile and compacted chromatin do not qualify
  • Oligodendroglioma-like regions often in pilocytic astrocytomas and dysembryoplastic neuroepithelial tumors and in these settings are considered part of diagnosis
Variants
  • Two distinct genetic variants5
  • The first:
    • often composed mainly of classic oligodendrogliomatous elements
    • combined deletions of chromosomes 1p and 19q generally unaccompanied by TP53 abnomalities (like with most pure oligodendrogliomas)
      • more characteristic of oligoastrocytomas arising in frontal, parietal and occipital regions than those in temporal lobes or basal ganglia7
  • The second:
    • frequently astrocyte-predominant
    • exhibits TP53 mutations or loss of heterozygosity involving chromosome 17p with intact 1p/19q status (genotype characterizing most fibrillary and gemistocytic astrocytomas)

Mixed Oligodendroglial and Ependymal Tumors

  • May be clear cell components:
    • histologically identical to oligodendroglioma within conventional ependymomas, particularly if supratentorial
    • retaining ependymocytic features ultrastructurally so questioning descriptions of mixed oligodendroglial and ependymal tumors3

Ependymoastrocytoma

  • Occasional diagnosis for other forms of mixed glial neoplasia:
    • infiltrative tumors of partially astrocytic aspect with foci of conspicuous pseudorosette formation
    • neoplastic cells often retain astrocytic nuclear features and elaborate cytoplasmic processes considerably coarser than those of classic ependymoma
  • Diagnosis should not be extended to common fourth ventricular ependymoma harboring minor components of astrocytic appearance

Differential Diagnosis

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Genetics

  • Isolated 1p/19q chromosomal deletions:
    • marker of chemosensitivity and prolonged survival when deleted in pure oligodendrogliomas8–10

References

1 Coons SW, Johnson PC, Scheithauer BW, Yates AJ, Pearl DK. Improving diagnostic accuracy and interobserver concordance in the classification and grading of primary gliomas. Cancer. 1997;79:1381–1393.

2 Donahue B, Scott CB, Nelson JS, Rotman M, Murray KJ, Nelson DF, et al. Influence of an oligodendroglial component on the survival of patients with anaplastic astrocytomas: a report of Radiation Therapy Oncology Group 83-02. Int J Radiat Oncol Biol Phys. 1997;38:911–914.

3 Hart MN, Petito CK, Earle KM. Mixed gliomas. Cancer. 1974;33:134–140.

4 Kim L, Hochberg FH, Thornton AF, Harsh GR, Patel H, Finkelstein D, et al. Procarbazine, lomustine, and vincristine (PCV) chemotherapy for grade III and grade IV oligoastrocytomas. J Neurosurg. 1996;85:602–607.

5 Maintz D, Fiedler K, Koopmann J, Rollbrocker B, Nechev S, Lenartz D, et al. Molecular genetic evidence for subtypes of oligoastrocytomas. J Neuropathol Exp Neurol. 1997;56:1098–1104.

6 Shaw EG, Scheithauer BW, O'Fallon JR, Davis DH. Mixed oligoastrocytomas: a survival and prognostic factor analysis. Neurosurgery. 1994;34:577–582.

7 Mueller W, Hartmann C, Hoffmann A, Lanksch W, Kiwit J, Tonn J, et al. Genetic signature of oligoastrocytomas correlates with tumor location and denotes distinct molecular subsets. Am J Pathol. 2002;161:313–319.

8 Cairncross JG, Ueki K, Zlatescu MC, Lisle DK, Finkelstein DM, Hammond RR, et al. Specific genetic predictors of chemotherapeutic response and survival in patients with anaplastic oligodendrogliomas. J Natl Cancer Inst. 1998;90:1473–1479.

9 Ino Y, Betensky RA, Zlatescu MC, Sasaki H, Macdonald DR, Stemmer-Rachamimov AO, et al. Molecular subtypes of anaplastic oligodendroglioma. Implications for patient management at diagnosis. Clin Cancer Res. 2001;7:839–845.

10 Smith JS, Perry A, Borell TJ, Lee HK, O'Fallon J, Hosek SM, et al. Alterations of chromosome arms 1p and 19q as predictors of survival in oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas. J Clin Oncol. 2000;18:636–645.

Last updated: 12 Feb 2006

Mixed Gliomas

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