Benign Bone Tumours

Classification

Histologic Type

• Osteogenic
  • Osteoid Osteoma
  • Osteoblastoma
• Chondrogenic
  • Chondroma
  • Enchondroma
  • Chondroblastoma
• Fibrogenic
  • Non-Ossifying Fibroma
  • Desmoplastic Fibroma
  • Chondromyxoid Fibroma
• Cystic
  • Unicameral Bone Cyst
  • Aneurysmal Bone Cyst
• Unknown origin
  • Giant Cell Tumour (GCT)
  • Langerhans Cell Histiocytosis (Eosinophilic Granuloma)

Enneking Classification of Benign Bone Tumours

Osteoid Osteoma

Epidemiology

• Men > Women
• 5–30 years old

Aetiology

• Unknown

Investigations

• X-Ray
  • <1 cm nidus with surrounding lucent ring and sclerotic rim
  • Extensive sclerosis, especially in the tibia
• Bone Scan
  • High uptake
• CT Scan
  • Necessary if sclerosis obscures nidus

Presentation

• Night pain
• Long-standing aching pain responsive to NSAIDs, especially aspirin

Location

• Anywhere, but most common:
  • Proximal femur
  • Tibial diaphysis
  • Posterior elements of the spine (painful scoliosis at apex of concavity)
  • Can be intra-articular (most common in hip joint)

Pathology

• Uniform osteoid seams
• No pleomorphism or invasion into surrounding bone

Management

• NSAIDs (lesion burns out in 2–3 years)
• RF Ablation under CT guidance (90% cure rate)
• Surgical excision (if other methods fail)

Osteoblastoma

Epidemiology

• Rare
• Commonly occurs in the 20s

Aetiology

• Unknown

Presentation

• Long-standing pain
• Less night pain and less responsive to NSAIDs
• Neurologic symptoms if in the spine

Location

• Long bones (metaphysis or diaphysis)
• Pelvis
• Proximal femur
• Posterior elements of the spine (scoliosis)

Pathology

• Similar to Osteoid Osteoma but larger and macroscopic differences

Imaging

• X-Ray
  • Sclerotic center with surrounding expanding lucent area
  • More extensive lucency than Osteoid Osteoma
  • May mimic malignant lesions
• CT Scan
  • Evaluates true extent
• Bone Scan
  • High uptake

Differential Diagnosis

• Osteoid Osteoma, Osteosarcoma, ABC, GCT
• 10–40% contain an ABC

Management

• Surgical due to locally aggressive nature
  • Marginal resection
  • Curettage and grafting

Paraosteal Osteoma

• Rare, benign, self-limiting tumor
• Grows on the bone surface like pedunculated osteochondroma
• Associated with Gardener’s syndrome (multiple osteomas, colonic polyps, fibromatosis)

Histology

• Mature lamellar bone

Bone Islands (Enostosis)

Aetiology

• Focal failure of endochondral ossification

Imaging

• Dense cortical, well-demarcated intramedullary lesion
• Low signal on T1 and T2 MRI, no surrounding edema

Management

• None if asymptomatic
• Surveillance or biopsy if diagnosis is unclear

Osteopikilosis

• Hereditary condition with multiple bone islands
• Autosomal dominant
• Associated conditions: syndactyly, dwarfism

Enchondroma

Aetiology

• Fragments of epiphyseal cartilage trapped in metaphysis during growth

Location

• Hands, long bones, proximal humerus, distal femur, tibia

Imaging

• Lytic area with chondroid matrix
• Calcification in long bones
• Causes cortical thinning and expansion in hands

Presentation

• Usually asymptomatic, incidental finding
• Pathologic fractures in hands

Management

• Intralesional curettage and grafting if symptomatic and isolated

Associated Conditions

• Ollier’s Disease (20–30% risk of malignant transformation)
• Maffuci’s Syndrome (100% risk of malignant transformation)

Periosteal Chondroma

• Benign tumor on the bone surface under the periosteum
• No malignant potential

Epidemiology

• Rare, occurs between 10–30 years

Management

• Marginal resection if symptomatic

Osteochondroma

Aetiology

• Benign cartilaginous tumor on the bone surface

Epidemiology

• Most common benign bone tumor
• Arises in children, identified in the first two decades of life

Location

• Around knee, proximal humerus, pelvis, posterior spinal elements

Presentation

• Mechanical symptoms from irritation

Management

• Excision if symptomatic or concerns about malignant transformation
• Associated with Multiple Hereditary Exostosis

Chondroblastoma

Epidemiology

• Males > Females
• Found in children and young adults

Location

• Epiphysis or apophysis (e.g., knee, pelvis, proximal humerus)

Imaging

• <4 cm, central in epiphysis with sclerotic rim

Management

• Intralesional curettage and grafting
• Phenol to lower recurrence rate (10%)

Chondromyxoid Fibroma

Epidemiology

• Rare, occurs in the 2nd or 3rd decade
• More common in males

Location

• Metaphyseal regions of long bones (lower limbs)

Management

• Intralesional curettage and grafting

Haemangioma

Epidemiology

• Asymptomatic in most cases

Location

• Vertebral bodies, skull, long bones

Management

• Symptomatic treatment only (e.g., embolization, kyphoplasty)

Non-Ossifying Fibroma (NOF)

Epidemiology

• Common in children aged 5–15 years

Location

• Lower limb long bones, especially distal tibia

Management

• Observation if asymptomatic
• Curettage and grafting if symptomatic

Desmoplastic Fibroma

• Rare, locally aggressive
• Wide excision recommended to minimize recurrence

Langerhans Cell Histiocytosis (Eosinophilic Granuloma)

Epidemiology

• 80% under 20 years, Men > Women

Imaging

• Punched-out lytic lesion, thick periosteal reaction

Management

• Low-dose radiation, curettage, or steroid injection

Cystic Lesions

Unicameral Bone Cyst (UBC)

• Painless, filled with serous fluid
• Pathologic fracture may occur
• Management: Injection, curettage, grafting

Aneurysmal Bone Cyst (ABC)

• Painful, locally aggressive
• May arise de novo or within other lesions
• Management: Curettage and grafting, embolization for pelvic/spinal lesions

Giant Cell Tumour (GCT)

Epidemiology

• Females > Males
• Age: 30–50 years

Features

• Benign but aggressive
• May metastasize to the lung (2%)

Location

• Around the knee, distal radius, spine, pelvis

Imaging

• Eccentric lytic metaphyseal lesion growing into the epiphysis

Management

• Curettage and grafting/cement
• Recurrence rate: 15%
• Embolization for spinal/pelvic lesions