LYTIC BONE LESIONS
Non agressive bone tumour in <20
1. Aneurysmal bone cyst
- benign expansile tumour-like bone lesions of uncertain aetiology, composed of numerous blood filled channels,
- 1/3 due to secondary lesion eg chondroblastoma, fibrous dysplasia
- Most commonly in METAPHYSIS in long bones.
- Radiographic features:
– Sharply defined, expansile osteolytic lesions, with thin sclerotic margins
– CT: fluid-fluid levels
– MRI: characteristic fluid-fluid levels exquisitely
– The presence of a solid component in MRI suggests that the ABC is secondary.
Fluid-fluid level in ABC
2. Unicarmeral bone cyst (simple bone cyst)
- Commonly in metaphysis in humerus or femur.
- Fallen fragment sign is characteristic if there is a pathological fracture.
Fallen fragment sign
- Rare benign cartilaginous neoplasms that characteristically arise in the epiphysis or apophysis of a long bone in young patients.
- Location: EPIPHYSIS of long bones
- Calcium deposition surrounding the chondroblasts, which are typically polyhedral shape, results in typical “chicken-wire calcification” (pathognomonic).
- Radiographic feature, well defined lytic lesion with a sclerotic margin.
4. Fibrous cortical defect
- Most common bone tumour in children, regresses after bone maturity
- Most common location: metaphysis with SUBCORTICAL location
- Histologically similar to NOF: more bubbly appearance in radiograph
5. Eosinophilic granuloma
- Histocytosis X, Hands-Schuller-Christian disease
- Skeletal system is the most common site of involvement in LCH, and in 70% is the only organ system involved,
- Bone marrow locations (!) – skull, flat bones, vertebrae, pelvis, as well as femur and humerus.
- Radiographic features:
– Button sequestrum (small sequestrum of devascularised bone surrounded by lucency, classically described in osteomyelitis and eosinophilic granuloma but also can be found in lymphoma)
– Bevelled edge sign: uneven involvement of inner and outer layer –> resulting in a formation of two different lucent lesions of unequal size overlying each other
– Floating teeth sign: teeth ‘hanging in the wind’ as a result of alveolar bone destruction around the root
– Verterbra plana: vertebral body has lost almost its entire height anteriorly and posteriorly. most common cause in children, can regrow with treatment
6. Fibrous dysplasia
- Mono-ostotic or poly-ostotic (McCune-Albright syndrome: cafe au leit spots (coast of Maine) + endocrinopathy)
- Ground glass bone matrix, can be cystic and bubbly
- Most common locations:
– ribs (especially for mono-ostotic-most common rib expansile lesion)
– femur, tibia, pelvis (for poly-ostotic and mono-ostotic)
Non aggressive bone tumours 20-40
1. Giant cell tumour (osteoclastoma)
- Most common location: subarticular (from metaphysis extending into EPIPHYSIS in bones around the knee, distal radius – <20 think chondroblastoma)
- Locally invasive
- 4 classical features:
– occurs only with a closed growth plate (mature bone)
– well defined with non-sclerotic margin (though < 5% may show some sclerosis)
– eccentric: if large this may be difficult to assess
2. Herniation pit of femoral neck
- Incidental finding, DONT TOUCH LESION
- It represents a herniation of synovium or soft tissues into the bone through a cortical defect
Non aggressive bone tumour after 40
- MM, metastasis
- Herniation pit of femoral neck
BLASTIC BONE LESIONS
- Benign cartilaginous bone lesion
- Most common location is in small and large tubular bones, commonly in metaphysis
– Small: purely lytic
– Large: can have chondroid matrix (rings and arcs)
- Echondroma vs chondrosarcoma
2. Osteoid osteoma, osteoblastoma
- They have characteristic lucent nidus less than 2 cm and surrounding solid periosteal reaction and classically cause night-pain that is relieved by the use of salicylate analgesia.
- The nidus releases protaglandins (via Cox-1 and Cox-2) which in turn result in pain
- Most common in long bones
- If happens in spine is called osteoblastoma.
- Can be part hereditary multiple exostoses (HME): multiple osteochondromas
- Osteochondromas are considered a chondroid neoplasm and are essentially a part of the growth plate which separates and continues growing independently, without an associated epiphysis, usually away from the nearby joint. The medullary cavity is continuous with the parent bone, and they are capped by hyaline cartilage.
- Most common locations: lower limbs (femur and proximal tibia), upper limbs (humerus)
- Radiographic feature: sessile or pedunculated lesion pointing away from the epiphysis with a thin cartilage cap.
- As they represent normal growth of a growth plate in an abnormal direction, they often stop growing with the rest of the skeleton. In most instances no treatment is required. The osteochondroma can be locally resected for cosmetic or mechanical reasons.
- Malignant transformation is not usual. Can be suspected by remembering GLAD PAST
– Growth after maturity
– Lucency (new)**
– Add.scintigraphic activity
– Destruction (cortical)**
– Pain after puberty
– Soft tissue mass
– Thickened cartilage cap >1.5 cm**
- Bone infarction (eg sickle cell disease): osteonecrosis or medullary infarct
– Subchondral infarct is called AVN
– Radiographic feature: metaphysis and medullary(often will be centric), normally serpiginous
- Chronic osteomyelitis
- Metastasis (ivory vertebrae): lymphoma, paget’s disease, prostate
** if in kids, consider lymphoma, osteoblastoma, mets from neuroblastoma