4 x 5 cm juxta articular lesion right tibial proximal metastasis.  Thinning cortex proximally and posteriorly.  Radiology appearances suggestive of giant cell tumour.  Largely empty cavity with some lining curettage for specimen.  

Right tibia, tissue from cystic cavity juxta-articular proximal tibia
Multiple gritty fragments measuring up to 8 mm.  All processed for decalcification.  
Sections show multiple fragments of a bone tumour composed of plump oval histiocytoid cells with scatterd osteoclast-like giant cells. Within the cellular tissue there are islands of chondroid/cartilage. The appearances are consistent with those of a chondroblastoma.