Giant Cell Tumour

Osteoclastoma

Epidemiology and Etiology:

· 20s to 40s

·

Common sites:

· Knee (distal femur / proximal tibia)

Gross features:

· Epiphyseal almost always

· Metaphyseal in adolescents

· Large

· Red-brown

· Cystic degeneration frequently

· X-ray:

· Lytic

· Well-delineated but not sclerotic edges

· Eccentric

· Erode into the subchondral bone plate

· Overlying cortex frequently destroyed

· Thin shell of reactive bone

· Solitary usually

Histologic features:

· Uniform oval mononuclear cells with indistinct cell membranes (syncitial pattern)

· Numerous scattered multinucleated giant cells, osteoclast type

· 100 or more nuclei

· Identical features to those of the mononuclear cells

· Frequent mitoses

· Necrosis common

· Hemorrhage common

· Hemosiderin deposition common

· Reactive bone formation common

Immunophenotype:

Marker:

Sensitivity:

Specificity:

· Monocyte-macrophage lineage

Molecular features:

·

Other features:

· Benign but locally aggressive

· Local recurrence

· Metastasis to lungs (4%)

· Sarcomatous transformation is rare

· Arthritic symptoms commonly

· DDx:

· Brown tumour of hyperparathyroidism

· Giant cell repairative granuloma

· Chondroblastoma

· PVNS

References:

· Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004.