 (1) Location of the lesion  (2) Extent of the lesion  (3) What is the lesion doing to the bone?  (4) What is the bone doing to the lesion?  (5) Hint as to its tissue type / matrix

 Location and age of patient most important parameters in classifying a primary bone tumor.  Simple to determine from plain radiographs.

 EPIPHYSEAL ◦ Chondroblastoma ◦ Clear cell chondrosarcoma ◦ Giant cell tumor ◦ Aneurysmal bone cyst ◦ Geode (subchondral cyst) ◦ Infection ◦ Eosinophilic granuloma  DIAPHYSEAL ◦ Adamantinoma ◦ Leukemia, Lymphoma, Reticulum cell sarcoma ◦ Ewing sarcoma ◦ Metastasis ◦ Osteoblastoma/ osteoid osteoma ◦ Nonossifying fibroma  METAPHYSEAL ◦ Nonossifying fibroma (close to growth plate) ◦ Chondromyxoid fibroma (abutting growth plate) ◦ Solitary bone cyst, ABC, GCT ◦ Osteochondroma ◦ Brodie abscess ◦ Osteogenic sarcoma, chondrosarcoma

 Central: Enchondroma  Eccentric: GCT, CMF, osteosarcoma  Cortical: osteoid osteoma, NOF  Parosteal: osteochondroma, parosteal osteosarcoma

BONE TUMORCOMMONEST SITE SBCProximal humerus > prox. Femur ABC, GCT, OsteosarcomaLowerend femur > upper end tibia EnchondromaMetaphysis of small bones of hand & feet OsteochondromaDistal femur> prox. Tibia > prox. Humerus ChondroblastomaProximal humerus> prox femur Ewing’sFemur > fibula > tibia AdamantinomaMandible > tibia MyelomaVertebra Fibrous dysplasiaRibs > Upper femur > Tibia > lower femur Osteoid osteomaFemur > tibia ChordomaSacrum > clivus (spheno occipital) > anterior vertebral body Ivory osteomaFrontal sinus Chondromyxoid fibromaTibia > femur ChondroblastomaPelvis > femur OsteoblastomaPosterior spine

Patterns of bone destruction:  Lytic  Sclerotic PERMEATIVE GEOGRAPHIC MOTHEATEN Poorly demarcated lesion imperceptibly merging with uninvolved bone Long zone of transition Areas of destruction with ragged borders. Less well defined / demarcated lesional margin Longer zone of transition Well-defined smooth / irregular margin Short zone of transition

 Margin between tumor and native bone is visible on the plain radiograph.  Slowly progressive process is “walled-off” by native bone, producing distinct margins.  Rapidly progressive process destroys bone, producing indistinct margins.

 Margin types 1A, 1B, 1C, 2, and 3 ◦ least aggressive 1A, to most aggressive 3  Aggressive lesions destroy bone.  Aggressiveness increases likelihood of malignancy. ◦ BUT, not all aggressive processes are malignant. ◦ AND, not all malignant diseases are aggressive.

Margins: 1A,1B,1C increasing aggressiveness A well circumscribed lesion with a narrow zone of transition

 simple cyst (UBC)  enchondroma  FD  chondroblastoma  GCT  chondrosarcoma (rare)  MFH (rare)

 GCT  enchondroma  chondroblastoma  myeloma, metastatsis  CMF  FD  chondrosarcoma  MFH

 chondrosarcoma  MFH  osteosarcoma  GCT  metastasis  infection  EG  lymphoma

 myeloma, metastases  infection  EG  osteosarcoma  chondrosarcoma  lymphoma Multiple scattered holes that vary in size & seem to arise separately

 Ewing  EG  infection  myeloma, metastasis  lymphoma  osteosarcoma Poorly demarcated from normal, numerous elongated holes/slots in cortex, run parallel to long axis of bone

 Limited responses of bone Destruction:lysis (lucency) Reaction:sclerosis Remodeling:periosteal reaction  Rate of growth determines bone response ◦ slow progression, sclerosis prevails ◦ rapid progression, destruction prevails

 Periosteal reaction must mineralize to be seen on X ray ( 10 days – 3 weeks)  Configuration of periosteal reaction ◦ Nature of inciting process ◦ Intensity ◦ Aggressiveness ◦ Duration

 Thick, uninterrupted ◦ long standing process, often non-aggressive  stress fracture  chronic infection  osteoid osteoma  Spiculated, lamellated ◦ aggressive process ◦ tumor likely

periosteal reaction tumor advancing tumor margin destroys periosteal new bone before it ossifies Codman Triangle

Sunburst Appearance

 “Matrix” is the internal tissue of the tumor  Most tumor matrix is soft tissue in nature. ◦ Radiolucent (lytic) on x-ray  Cartilage matrix ◦ calcified rings, arcs, dots (stippled) ◦ enchondroma, chondroblastoma, chondrosarcoma  Ossific matrix ◦ osteosarcoma

Exostosis: well defined bony projection growing away from physis Cartilage maybe calcified if lesions are large / malignant change

 Nidus: a tiny radiolucent area  If in diaphysis  surrounded by dense bone and thickened cortex Metaphysis  less cortical thickening  Double density sign on bone scan – increased uptake in nidus and decreased uptake in reactive sclerotic zone (also seen in Brodie’s abcess)  Lytic nidus surrounded by sclerotic bone in CT  Centre of nidus may be calcified

 Well demarcated osteolytic lesion sometimes containing flecks of calcification  Less reactive bone than osteoid osteoma  Bone scan - intense activity

 Cystic radiolucency on the diaphysial side of the growth plate  Cortex may be thinned and bone expanded with well defined thin sclerotic margin  May have pseudo-loculated appearance secondary to irregular cortical thinning and thin septal ridges  Falling fragment sign typical and the lesion is never wider than epiphysial plate  Bone scan cold or minimal activity unless fractured

 Gross honey comb lesion  Often eccentrically placed  Does not extend to the joint (unlike GCT)  Warm to hot on bone scan

 Usually well defined geographic lytic lesion in the epiphysis/metaphysis extending up to the joint surface without marginal sclerosis  Junction with normal bone often poorly defined  Cortex thinned and sometimes ballooned  Bone scan warm to hot

Fibrous cortical defect  Margin well defined, sometimes scalloped and often sclerosed

Non-ossifying Fibroma

 Ground glass appearance typical  Shepherds crook deformity of proximal femur  Variable appearance with expansion of cortex

 Scalloped erosions on endosteal surface  May have flecks of calcification

 Rounded or oval rare area  Usually eccentrically placed  May cross the growth plate  Sharp outline and sclerotic rim  Scalloped margin and thin cortex

 Well defined area of rarefaction eccentrically placed in the epiphysis or across the growth plate  No reaction in surrounding bone  50% show central calcification, 50% show linear periosteal reaction  Bone scan increased uptake at margins

 Multiple loose bodies

 Large osteolytic lesion in the midline  May contain flecks of calcification  Marked bone destruction

 Diffuse osteopenia with multiple osteolytic lesions dispersed throughout skeleton.

 Characteristic honey comb appearance in diaphysis  Cortical thinning with expansion

 Vertical striations without bone expansion and coarse trabecular appearance (corduroy appearance)

 Mottled lytic defect usually no sclerotic rim  May destroy cortex  Usually endosteal or periosteal reaction  Lesions in flat bones and ribs appear punched out  May appear loculated due to sparing of large trabeculae  Spinal lesions- collapse (vertebra plana), which may heal

 Mottled or moth eaten lesion diffusely involving bone  Lytic destruction common, often the cortex is perforated  Onion skin appearance- layers of periosteal new bone are said to be characteristic  May form Codman’s triangle

 Variable with combination of bone destruction and bone formation  Sun ray spicules/ sun burst appearance and Codman’s triangle may be evident  Cortical breach common  Adjacent soft tissue mass  Joint space rarely involved ◦ 25% Lytic ◦ 35% Sclerotic ◦ 40% Mixed  Telangiectatic type- purely lytic

 Variable appearance with % have calcification and 50% have sub periosteal new bone  May be a large cystic lesion with cortical destruction and central calcification, endosteal scalloping and cortical expansion; annular, punctate or comma shaped calcification

 Bone often mottled or moth eaten with extension into soft tissue  Osteolytic lesion may be surrounded by reactive bone  Destructive appearance radiologically  Usually little periosteal reaction

 Osteolytic commonest - cortical destruction with little or no periosteal reaction; Lungs, Kidney, Adrenal, Thyroid, Uterus  Osteoblastic deposits – Prostate, Bladder, Testis, Breast and Bowel secondaries. Also carcinoid lung tumors, lymphoma  Mixed- Breast, Lung, Ovary, Cervix  Lymphoma deposits may resemble prostatic deposits, i.e. sclerotic secondaries  Lytic, expansile, with soft tissue mass- RCC, thyroid  X-Ray- at least 50% loss of bone to produce lysis on X-ray, Loss of single pedicle produces a “winking owl sign”. CT scan, MRI

Osteolytic bone metastases: breast carcinoma shows multiple osteolytic bone lesions.

Osteoblastic bone metastases

Mixed pattern bone metastases:

 Early - vague mottled lucent areas  Diffuse destructive lytic lesion with little periosteal reaction  Usually combination of patchy sclerosis and mottled destruction  Hogkins disease - typical appearance of ivory vertebrae

 May be generalised decrease in bone density  Multiple punched out defects  Little bony reaction around lesions  Solitary lesion = plasmacytoma; multilocular expanding lytic lesion in a red marrow area  Frequently cold on bone scan