diffuse astrocytoma (WHO grade 2)

Introduction

Grade 2, most commonly fibrillary astrocytoma.

Epidemiology

• 18% of primary brain tumors
• most common in late middle age

Pathology

• marked tendency to become more anaplastic with time
  • a tumor initially diagnosed as a diffuse astrocytoma frequently proves on later biopsy to be anaplastic astrocytoma or glioblastoma

Microscopic pathology

• well differentiated neoplastic astrocytes on a background of loosely structured sometimes microcystic tumor matrix
• moderately increased cellularity
• occasional nuclear atypia
• mitotic activity generally absent; single mitosis does not increase grade
• no necrosis or vascular proliferation
• fibrillary astrocytoma: most common
• gemistocytic astrocytoma
• protoplasmic astrocytoma:

Immunophenotype

• GFAP +
• vimentin +
• S100 +
• Ki67/MIB1 usually < 4%; <1% for protoplasmic variant

Genetics

• Ras mediated signal transduction involved in initiation of astrocytoma development however ras mutations have not been identified
• PDGF/PDGFR expression elevated in every grade of astrocytic neoplasm

Management

• surgical excision
  • should be performed if feasible
  • may relieve symptoms
• post-operative radiation therapy (indications uncertain)
• no role for chemotherapy
• prognosis: 93 months

Also see further descriptions under astrocytic neoplasm and subtypes.

More general terms

• astrocytoma (astrocytic neoplasm)

More specific terms

• fibrillary astrocytoma
• gemistocytic astrocytoma
• protoplasmic astrocytoma