Osteoblastom

Osteoblastomas are rare bone-forming tumors that may be locally aggressive. They are larger (>1.5-2 cm) and tend to affect the axial skeleton more often than their histologic relative, osteoid osteoma.

Epidemiology

They account for 1-3% of all primary bone tumors . Patients typically present around the second to third decades of life. There is a recognized male predilection with a male to female ratio of approximately 2.5:1.

Clinical presentation

With spinal lesions, painful scoliosis is a common presenting symptom. Otherwise, it presents with an insidious onset of dull pain, worse at night, with minimal response to salicylates (only 7% of patients respond, unlike osteoid osteoma). The area will characteristically be swollen and tender with a decreased range of motion.

Pathology

Osteoblastoma is histologically similar to an osteoid osteoma but they are larger. They are bone- and osteoid-forming and is comprised of osteoblasts. There is high associated vascularity.

Location

• spinal column: ~40% (range 32-46% ); often involves the posterior column
  • cervical spine: 9-39% of all spinal lesions  
  • sacrum: 17% of all spinal lesions
• usually located in the metaphysis and distal diaphysis of the long bones

Variants

• aggressive (malignant) osteoblastoma: has a high of number epithelioid osteoblasts with nuclear atypia

Radiographic features

Osteoblastomas can have a wide range of radiographic patterns. Lesions are typically larger than 1.5-2 cm in size although smaller lesions may occur .

Plain radiograph

• lesions are predominantly lytic, with a rim of reactive sclerosis
• tend to be expansive
• internal calcification may sometimes be present
• an associated soft tissue mass may also be present
• demonstrate a rapid increase in size with associated cortical expansion in the vast majority of patients, sometimes with cortical destruction
• there may be surrounding sclerosis or periostitis in up to 50%
• there may be a secondary aneurysmal bone cyst in 20%

CT 

• similar to the radiograph, lesions are often demonstrated as predominantly lytic 
• internal matrix mineralization is better appreciated on CT

MRI

MRI features tend to be non-specific and often overestimate the lesion :

• T1: typically hypo to isointense on T1 with areas of decreased intensity that correspond to foci of calcification
• T2: typically isointense to hypointense on T2 with foci of decreased intensity corresponding to the foci of calcification
  • a high signal may be seen in surrounding bone marrow and soft tissues due to edema "flare phenomenon" 
• C+ (Gd): this is a highly vascular tumor and therefore typically avidly enhances, with associated enhancement of the surrounding soft tissues

Nuclear medicine

• Tc-99m MDP or HMDL: often shows intense uptake although this is non-specific and is typical in all lesions exhibiting increased bone turnover

Treatment and prognosis

Radical surgical excision is often the treatment of choice. Pre-operative embolization is commonly carried out to reduce bleeding risk although surgery needs to be performed at a very short time interval in order to avoid reconstitution of collateral blood supply. Percutaneous ablation is an emerging modality for treatment of these lesions (as well as osteoid osteoma) .

Complications

Lesions are prone to extensive intraoperative bleeding due to intrinsic vascularity.

Differential diagnosis

• osteoid osteoma: <1.5-2 cm

Siehe auch:

• Osteoid-Osteom
• Chondroblastom
• Knochentumoren
• Osteoblastom der Wirbelsäule

und weiter:

• vertebrale Metastasen
• Osteom NNH
• Skoliose
• Multiples Myelom
• kortikales Desmoid
• Enchondroma protuberans
• epiphysäre Knochentumoren
• solide Periostreaktion
• Tumoren der Nasennebenhöhlen
• solitary sclerotic bone lesion
• ivory vertebra sign
• osseous lesions preferentially involving the epiphysis
• Knochenläsionen der Epiphyse
• lytic bone lesion (mnemonic)
• Plasmozytom des Knochens solitär
• ring- und bogenförmige Verkalkungen
• spinale Metastasen
• posterior vertebral body lesions (mnemonic)
• radiologisches muskuloskelettales Curriculum
• primary tumours of the spine
• osteoid lesions
• solitary sclerotic bone lesion with a lucent centre
• bone-forming tumours
• lytic bone lesion surrounded by marked sclerosis (mnemonic)
• Läsionen des Sakrums
• Knochenläsionen mit Sequester
• Osteoblastom der Halswirbelsäule
• Sklerosierung der Klavikula
• Knochenläsionen der Metaphyse
• spikulierte Periostreaktion
• Osteoidosteom der Wirbelsäule
• vertebral osteoblastoma
• osteoblastoma sacrum
• osteoblastoma of occipital bone
• osteoblastoma of hamate
• osteoblastoma of the radius
• osteoblastoma of the skull
• knochenbildende Tumoren