This document discusses osteoid osteoma, a relatively common benign bone tumor. It is characterized by a small nidus less than 1.5 cm in diameter that typically causes persistent night pain relieved by salicylates. Diagnosis is usually made through imaging like CT or MRI that identify the central nidus. Treatment options include long-term anti-inflammatories, percutaneous radiofrequency ablation to destroy the nidus, or surgical removal of the nidus through curettage or en bloc resection. The document also briefly discusses other bone forming tumors like osteoblastoma, osteoma, and their signs, symptoms, diagnosis and treatment.

1. BONE FORMING TUMOR
Dr. Rabins Kumar Sah
Department of Orthopaedics
1st Year Resident
NMCTH, Birgunj

2. A classification of bone tumours. Modified after
Revised WHO Classification –Schajowicz (1994)

3. Osteoid osteoma
 Relatively common lesion of bone (4% of all primary bone
tumors excluding myeloma).
 10% of all benign bone lesions
 Characterized by nidus of osteoid tissue. <1.5 cm in
diameter.
 Cytogenetic analysis of osteoid osteoma showed clonal
chromosomal changes(22q13 )
Symptoms:
 Persistent pain usually worse at night and Typically the
pain is relieved by salicylates .
 If the diagnosis is delayed a limp or muscle wasting and
weakness; spinal lesions may cause intense pain, muscle
spasm and scoliosis.

4. Osteoid osteoma cont...
 When the lesion is near joint - swelling, stiffness,
and contracture may occur.
Classifications:
 Depending on its location in the particular part of
the bone, the lesion can be classified
 Cortical
 medullary (cancellous)
 subperiosteal.
 It can be further sub-classified as extra- or
intracapsular (intraarticular).

5. Diagnosis
Radiology
 Imaging studies usually are diagnostic.
 Biopsy rarely is needed to confirm the diagnosis. The
lesion consists of a small (<1.5 cm) central nidus with
surrounding bony sclerosis.
 Plain radiographs often are sufficient to make the
diagnosis.
 CT is the best study to identify the nidus and confirm
the diagnosis.
 The lesions show increased uptake on technetium bone
scans.
 MRI usually shows extensive surrounding edema

6. Differential Diagnosis
Osteoblastoma
 Are larger: > 2 cm.
 Periosteal reaction may be more prominent than
encountered in osteoid osteomas
Stress fracture :
 Linear Radiolucency runs perpendicular or at an angle to
cortex.
 Scintigraphy- increased uptake of radiotracer (Double
density sign)
 Features of bone repair: osteoid and cartilaginous callous,
osteoblastic and osteoclastic activity.

7. Differential Diagnosis…
Bone abscess (Brodie):
 Irregular outline.
 Radiolucency, usually with a sclerotic rim, associated with
serpentine, linear tract. Predilection for metaphysis and the ends
of tubular bones.
 Scintigraphy- increased uptake of radiotracer.
 MRI
-T1 WI a well-defined low-to-intermediate-signal lesion outlined
by low-intensity rim.
-T2 WI a very bright homogenous signal, outlined by low-signal
rim.
 Necrotic tissue, giant cells, granulocytes, lymphocytes, plasma
cells, and histiocytes.

8. Differential diagnosis…
Bone island (enostosis)
 Homogeneously dense, sclerotic focus in cancellous bone
with distinctive radiating streaks (thorny radiation) that
blend with the trabeculae of the host bone.
 Scintigraphy- usually no increased uptake.
 MRI low-intensity signal on T1 and T2 WI.
 Focus of mature, compact bone with thickened peripheral
trabeculae that blend with trabeculae of the spongiosa.
-Wide bands of parallel or concentric lamellae
-Marrow spaces resembling Haversian canals.

9. Differential diagnosis…
Intracortical osteosarcoma
 Intracortical radiolucent focus surrounded by zone of
sclerosis. Occasionally central “fluffy” densities. Cortex
thickened or bulged.
 Scintigraphy increased uptake of radiotracer .

10. Pathology
 Microscopy shows fibrovascular tissue with immature
bony trabeculae that are rimmed by prominent osteoblasts.
 The appearance is similar to that of an osteoblastoma with
the exception that osteoblastomas are larger.
 The lesion usually is surrounded by a sclerotic rim. There is
no nuclear atypia.
 Osteoclasts and occasional giant cells can be seen.
 There are no aggressive features.

11. Treatment
Medical treatment :
 Long term anti-inflammatory.
 Spontaneous healing of the lesion occurs within 3 to 4
years.
Percutaneous radiofrequency ablation:
 Lesions of the pelvis or long bones of the extremities
can be treated .
 This technique involves a CT-guided core needle biopsy
after which a radiofrequency electrode is inserted
through the cannula of the biopsy needle.
 The temperature at the tip is increased to 90°C for 6
minutes.

12. Percutaneous radiofrequency ablation...
 It is done as an outpatient procedure, and patients
usually can return immediately to full activity.
 Recurrence rates are less than 10%.
 contraindications for lesions of the spine or lesions of
the small bones of the hands or feet.

13. Open surgical procedures
 Surgical management involves removal of the entire
nidus by curettage or en- bloc resection.
 Low recurrence rate but is rarely indicated for lesions
in the long bones because of an increased risk of
postoperative pathological fracture.
 Removal is done using the burr-down technique:
 This method consists of identifying the nidus intra-
operatively with fluoroscopy and using a power burr to
remove the sclerotic bone directly over the nidus.

14. Burr down technique
 Rarely, intraoperative bone scanning is needed to
identify the nidus.
 The nidus is removed using curets and sent for
pathological examination.
 The cavity is treated again with the power burr to
ensure that the entire nidus has been removed.
 In this manner, only the minimal amount of
surrounding reactive bone is removed ,minimizing the
risk of subsequent fracture.
 Recurrence rates are less than 10%.

15. Complications:
 Radicular irritation .
 Psychic depression.
 Entrapment neuropathy(posterior interosseous
neuropathy following osteoid osteoma of upper end of
ulna.

16. Osteoblastoma
 Rare bone-forming neoplasm <1% of bone
tumors in the Mayo Clinic series
 40% to 50% of the lesions- located in spine.
 Similar to an osteoid osteoma but larger (>2
cm diameter)
 More cellular and ominous in appearance.
 The tumor is slow growing, and symptoms
may be present for 1 to 2 years before a
diagnosis is made

17. Symptoms
 Pain is the most common symptom
- worse at night and relieved by NSAID’s.
 In spine- painful scoliosis or neurological deficit may
be present.
 Lumbar spine- signs and symptoms of nerve root
compression.
 Thoracic spine- cord compression is more common.

18. Types of osteoblastoma
1. Giant osteoid osteoma :

19. 2.Blow-out expansion
A: Several small central opacities in the lamina of C6 (arrows).
B: Large osteoblastoma originating in the lamina and involving
the pedicle, transverse process, and half of the vertebral
body of L5 (arrows) shows aneurysmal-like expansion with
central radiopacities.

20. 3.Aggressive
Dorsovolar (A) and lateral (B) radiographs of the right
hand shows aggressive osteoblastoma. very similar in
appearance to osteosarcoma, the lesion appears to be
contained by a shell of periosteal new bone.

21. 4.Periosteal :
 Anteroposterior radiograph showing juxtacortical
lesion of the mandible.

22. Diagnosis
Radiology:
 Radiographic appearance is nonspecific.
 Lesion may be radiolucent, sclerotic, or mixed.
X-Ray :
 Classic appearance of a calcified central nidus
with a surrounding radiolucent halo and reactive sclerosis
Radioisotope scan:
Reveals ‘hot’ area
MRI :
 Extension into the soft tissue is rare except in the spine.

23. Microscopically
 Lesion resembles an osteoid osteoma.
 It contains a fibrovascular stroma with production of
osteoid and primitive woven bone.
 Bony trabeculae are lined by a single layer of
osteoblasts, which may be important in differentiating
osteoblastoma from osteosarcoma.
 Features favoring an osteoblastoma include sharp
circumscription and a loose arrangement of the tissue.
 Features favoring a malignant diagnosis include
permeation of surrounding tissue and sheets of
osteoblasts without bone production.

24. Differential Diagnosis
 Osteoid osteoma
 Aneurysmal bone cyst :
 Blow-out, expansive lesion.
 In long bone buttress of periosteal reaction.
 This shell of reactive bone frequently covers the lesion, but
may be absent in rapidly growing lesions.
 Soft tissue extension may be present
 Multiple blood-filled sinusoid spaces separated by fibrous
septae displaying lamellae of primitive woven bone.
 May contain hemosiderin and reactive foam cells; solid areas
composed of fibrous elements containing irregular bone
trabeculae and giant cells, sometimes in great numbers.

25. Differential diagnosis
Osteosarcoma
 Permeative or moth-eaten bone destruction.
 Wide zone of transition
 Tumor-bone in form of cloud-like opacities
 Aggressive periosteal reaction & soft tissue mass.
 Microscopy
-Permeation of cortical bone
-Attenuation and “trapping” of lamellar bone
-Atypical mitoses or anaplasia, hyperchromatism and
pleomorphism of cells and nuclei
-Tumor bone and tumor cartilage formed by malignant
cells.

26. Treatment
 Excision and bone grafting.
 Radiotherapy for inaccessible lesions, e.g. vertebrae.
Complications:
 Excision of lesions in the vertebral pedicle or the floor
of the acetabulum is not easy and may be incomplete
so, local recurrence is common and may turn to
malignant.

27. Osteoma (Ivory Exostosis)
 Rare benign tumour
 Appears as localized
thickening on the outer or inner surface of
compact bone.

28. Symptoms
 An adolescent or young adult presents with a painless,
ivory-hard lump, on the outer surface of the skull,
subcutaneous surface of the tibia.
 Inner table lesion of skull- may cause focal epilepsy
 It may protrudes into the paranasal sinuses.

29. Diagnosis
 Conventional radiography- basis for the diagnosis of
osteoma.
 X-ray: a sessile plaque of exceedingly dense bone with
a well circumscribed edge .

30. Computed tomography :
 Effective in demonstrating lack of cortical invasion. .

31. Differential Diagnosis:
 Parosteal osteosarcoma:
 Long history, absence of pain and smooth outline will
dispel this suspicion.
 Foreign Body(e.g. Bullet)

32. Treatment :
 Indication
-Pressure symptoms
-cosmetic reasons. Excision with normal margin
Complications :
 Mainly cosmetic problems.
 Very rarely early intracranial pressure symptoms.

33. References
 S. Terry Canale ,James H.Beaty: Campbell's Operative
Orthopaedics. 12th edition. Mosby,an imprint of Elsevier Inc.
2013.
 Louis Solomon, David Warwick, Selvadurai Nayagam. Apley’s
System of Orthopaedics and Fractures.9th edition. Hodder
Arnold, an imprint of Hodder Education, an Hachette UK
Company,338 Euston Road, London NW1 3BH:2010.
 Greenspan, Adam; Jundt, Gernot; Remagen, Wolfgang.
Differential Diagnosis of Orthopaedic Oncology, 2nd Edition.
Lippincott Williams & Wilkins: 2007
 Pandey sureshwar,pandey Anil kumar.clinical orthopaedic
Diagnosis.3rd edition.Jaypee Brothers Medical publishers(p)
Ltd.2009
 Kumar, Abas, Fausto. Robbins pathologic Basic Pathology .9th
edition . Elsevier.2012