Osteoid Osteoma
This is a benign bone tumour, usually of adolescence. It causes significant pain. Imaging demonstrates bone formation around a radiolucent nidus. The microscopic appearance is of activated osteoblasts located within the nidus. The nidus is always < 1 cm and larger tumours are osteoblastomas, which follow a locally aggressive course. Treatment is with NSAIDs or surgical excision of the nidus; the condition itself is often self limiting after a few years.
Osteoblastoma
These are larger tumours of osteoblasts that have the same microscopic appearance. They can cause deformation of surrounding bone and compression of adjacent structures. Treatment is with surgical excision of the nidus; if this is incomplete then adjuvant radiotherapy is offered (? dose)
Adamantinoma
Aside from having the coolest name for a cancer ever, adamantinomas are rare bone tumours that usually arise in the tibia. The lesion is lytic on plain x-ray. Microscopically, the tumour is comprised of epithelioid and osteofibrous regions. Treatment is with local surgical excision. About 20% of cases metastasise.
Giant Cell Tumour
This tumour forms about 4-5% of bone tumours and occurs in young adults. They form a lytic lesion within the end of a long bone, most often the femur or tibia. They can be locally aggressive but rarely metastasise. Surgical excision is curative in 50% of cases; radiotherapy is used when surgery would cause deformity. The dose is 50 Gy in 25 fractions.
