Primary bone tumors – Systematic pathology

Location in bone

a. Epiphysis:

1. Pediatric: Chondroblastoma
2. Adult: Giant cell tumor (GCT) or Osteoclastoma
3. Other differentials: Osteomyelitis, Paget disease

b. Metaphysis:

1. Medullary:
   • Simple (unicameral) bone cyst
   • Aneurysmal (multicameral) bone cyst
   • Enchondroma
   • Fibrous dysplasia
   • Chondromyxoid fibroma
   • Conventional osteosarcoma
   • Chondrosarcoma
   • Pediatric GCT or osteocalstoma
   • Osteochrondroma (most common benign bone tumor)
2. Cortical:
   • Fibrous cortical defect (FCD)
   • Non-ossifying fibroma (NOF)
   • Osteoid osteoma
3. Juxtacortical:
   • Juxtacortical chondroma
   • Periosteal osteosarcoma
   • Paraosteal osteosarcoma
   • Juxtacortical chondrosarcoma

c. Diaphysis:

Mnemonic: Diaphysis comes AFORE metaphysis and epiphysis.

1. Adamantinoma
2. Fibrous Dysplasia (Fibrous bone tumor originating in diaphysis; “D” for dysplasia and dipahysis; all other fibrous tumors in metaphysis)
3. Osteoid osteoma and Osteoblastoma
4. Round cell lesions (Ewing sacrcoma, Myeloma, Reticulum cell sarcoma)
5. Enchondroma

1. Medullary:
   • Fibrous dysplasia
   • Ewing sarcoma
   • Endchondroma
2. Cortical:
   • Ossifying fibroma (Osseofibrous dysplasia)
   • Osteoid osteoma (<2 cm; pain relieved by NSAIDs) and Osteoblastoma (>2 cm; pain not relieved by NSAIDs)
   • Adamantinoma

Other medullary lesions which can occur in metaphysis or diaphysis

1. Localized Langerhans cell histiocytosis (LCH)
2. Myeloma
3. Metastases
4. Malignant vascular tumors
5. Lymphoma

2 Benign tumors that metastasize:

1. Giant cell tumor
2. Chondroblastoma

Location in Human body

1. Adamantinoma: Tibia or Mandible (ameloblastoma)
2. Osteoid osteoma: Proximal femur > Tibia > Posterior spine
3. Osteoblastoma: Posterior spine > Long bones
4. Osteoma: Facial bones
5. Fibrous dysplasia: Proximal femur > Tibia , Ribs (most common site in mono-ostotic FD), Craniofacial skeleton
6. Ewing’s sarcoma: Femur > Tibia
7. Simple bone cyst: Proximal humerus > Proximal femur
8. Aneurysmal bone cyst (ABC): Proximal femur > Tibia, Posterior spine, Pelvis
9. Osteosarcoma: Distal femur > Proximal tibia
10. Chondrosarcoma: Pelvis > Femur > Ribs > Humerus > Tibia
11. Enchondroma: Small bones of hand and feet
12. Osteochondroma (Exostosis): Distal femur
13. Ivory osteoma (Eburnated osteoma): Frontal sinus
14. Non-ossifying fibroma: Tibia
15. Chondroblastoma: Distal femur and proximal tibia > Proximal humerus > Flat bones
16. Giant cell tumor: Distal femur and proxima tibia
17. Hemangioma: Anterior spine
18. Myeloma: Anterior spine
19. Glomus tumor: Tuft of phalanx
20. Chordoma: Sacrum > Clivus > Anterior spine

In vertebra:

1. Posterior part: Benign condition
2. Anterior part: Malignant condition (Exception: Hemangioma and Eosinophilic granuloma)

Age group

a. <1: Neuroblastoma

b. 0-10: Ewing’s (tubular bones)

• Others: Solitary bone cyst (SBC)

c. 10-20: Osteosarcoma, Ewing’s (flat bones), Chondroblastoma, Osteoblastoma, Osteoid osteoma, Osteochondroma

• Others: SBC, ABC, NOF, Fibrous dysplasia, Chondromyxoid fibroma

d. 20-40: Giant cell tumor, Enchondroma, Osteoma, Osteoblastoma

e. >40: Metastatic, Myeloma, Chondrosarcoma

Lytic Expansile Soap Bubble Appearance

Mechanism: Cortical involvement with cortical tumors or medullary tumors that erode inner cortex but allows time to lay down new bone on outer cortex (not very aggresive).

Mnemonic: FEGNOMASHIC

1. Fibrous dysplasia
2. Enchondroma
3. Eosinophilic granuloma
4. Giant cell tumor
5. Nonossifying fibroma
6. Osteoblastoma, Osteosarcoma (telangiectatic)
7. Metastases
8. Myeloma
9. Aneursymal bone cyst
10. Simple bone cyst
11. Hyperparathyroidism (brown tumor)
12. Infection
13. Chondroblastoma
14. Chondromyxoid fibroma

Moth-eaten destruction of bone (Permeative lesion)

These are small patchy lytic lesions.

Mnemonic: FIRE MD

1. Fibrosarcoma
2. Infection
3. Round cell tumors (Ewing’s, neuroblastoma, retinoblastoma)
4. Eosinophilic granuloma
5. Myeloma
6. Desmoid tumor

Periosteal reaction

1. Solid or unilamellated: Non-aggressive lesion, periosteum has time to lay down thick bone (Osteoid osteoma)
2. Multi-lamerllated or onion-skin: Intermediate aggressive lesion (Ewings)
3. Spiculated, or “hair-on-end” (perpendicular to the cortex) or sunburst pattern: Most aggressive lesion (Malignancy)

Codman’s triangle: Elevation of periosteum away from the cortex. It may be seen in –

1. Conventional osteosarcoma
2. Ewing’s sarcoma
3. Osteomyelitis
4. Active aneurysmal bone cyst
5. Subperiosteal hematoma/abcess