This document provides a classification and overview of bone tumors, including: 1. A classification of primary benign and malignant bone tumors by histologic type, peak age, and common sites. 2. Descriptions of characteristic radiographic features that can help identify different tumor types. 3. Details on patterns of bone destruction, periosteal reaction, and matrix mineralization that are useful in tumor identification on imaging.

1. Classification of Bone Tumors
Rapid Review
Dpt. Aamir Memon
8/12/2013

2. Classification of primary benign bone tumors
Cartilage tumors Peak age (years) Most common sites Comments
Osteochondroma 10–30 M 2:1 (<20) Distal femur, proximal tibia, proximal humerus, rarely from
flat bones
> 2 cm cartilage cap may indicate malignant transformation.
Characteristic Radiographic Feature: Radio-opaque with Bony stalk capped with cartilage,
oriented away from involved joint
Enchondroma 10–40 Hands, feet, long tubular bones Characteristic Radiographic Feature: Radio-lucent expansion with well-defined margins.
Periosteal chondroma 10–40 Proximal humerus, distal femur, hip region, and pelvis Sharply demarcated from cortex
Chondroblastoma 10–30 Distal femur, proximal tibia and humerus, calcaneus Typically epiphyseal
Chondromyxoid fibroma 10–30 Proximal tibia, distal femur, pelvis, feet (metatarsal)
Osteogenic tumors
Osteoid osteoma 5–25 {M>F (<15)} Proximal femur, any long bones Distinguished from osteoblastoma by size and imaging
Characteristic Radiographic Feature: Radio-opaque with Lucent nidus surrounded by
sclerotic halo (“circle within a circle”).
Osteoblastoma 10–40 Spine, long tubular bones, jaws
Fibrogenic tumors
Desmoplastic fibroma 10–30 Mandible, femur, pelvis Very rare; distinction from FD, low-grade osteosarcoma, and fibrosarcoma may be difficult
Fibrohistiocytic tumors Diaphyseal or metaphyseal; rarely used concept, distinguished from nonossifying fibroma
only by clinical setting
Benign fibrous histiocytoma 20-60 Pelvis, femur
Giant cell tumor 20-45 {F 3:2} Distal femur, proximal tibia,
distal radius, sacrum
Characteristic Radiographic Feature: “Soap bubble appearance” in metaphysis, with
expansive some subarticular expansion.al; pulmonary metastases occur in 2%; very rarely
transformation to high-grade sarcoma
Vascular tumor
Hemangioma (cavernous,
capillary, epithelioid, etc.)
Classic
hemangiomas,
usually adults
Craniofacial bones, vertebrae Hemangiomas are often multicentric
Angiomatosis,
lymphangioma(tosis)
Often children Highly variable
Glomus tumor Usually adults Hands, distal phalanx
Hemangiopericytoma Usually adults Pelvis
Epithelioid
hemangioendothelioma
Adults Long tubular bones, spine
Soft tissue type tumors
Lipoma Adults Femur, calcaneus All very rare
Schwannoma Sacrum, mandible
Leiomyoma Mandible, tibia
FD fibrous dysplasia

3. Classification of primary malignant bone tumors
Histologic type Peak age (years) Most common sites Comments
Chondrosarcoma M 2:1 (40-60) Characteristic Radiographic Feature: Radio-lucent, with Lucent expansive lesion with well-defined border. Associated soft tissue reaction.
Primary 50–80 Pelvis, proximal/distal femur, proximal humerus, ribs Usually large, intraosseous; very rarely periosteal
Secondary 20–60 Ex osteochondroma(tosis): pelvis, hip and shoulder In Ollier’s/Maffucci’s at any site affected
Differentiated 50–70 Pelvis, femur, humerus Usually small component of low-grade chondrosarcoma juxtaposed with high-grade osteo-,
spindle cell-,MFH-, or other sarcoma
Clear cell 25–60 Proximal femur, humerus Typically epiphyseal location
Mesenchymal 10–40 Jaws, ribs, pelvis, spine 20–30% occur in soft tissues
Osteosarcoma M 2:1 (15-25) Characteristic Radiographic Feature: Radio-opaque (diffuse sclerosis) with poorly defined border with dense “ivory” (diffuse sclerosis) regions, soft tissue mass visible on x-ray.
Conventional 10–30 Distal femur, proximal tibia, hip and shoulder Typically metaphyseal
Telangiectatic osteosarcoma 10–30 Femur, tibia, humerus Typically metaphyseal; ABC-like, purely lytic
Low-grade central osteosarcoma 20–40 Distal femur, proximal tibia May dedifferentiate to high grade
Parosteal osteosarcoma 20–50 Posterior distal femur, proximal humerus May invade the bone, may dedifferentiate to high grade
Periosteal osteosarcoma 10–30 Femur, tibia Diaphyseal, surface lesion, predominantly chondroblastic, intermediate grade
High-grade surface 10–40 Distal femur, shoulder Diaphyseal or metaphyseal
Secondary osteosarcoma
Paget’s associated 50–90 Pelvis, hip and shoulder, Craniofacial High-grade osteosarcoma
Post-radiation 50–80 Pelvis, craniofacial, hip and shoulder, chest wall High-grade osteosarcoma
Other conditions 40–70 Bones affected by FD, bone infracts, chronic osteomyelitis,
etc.
Ewing´s sarcoma, PNET 5–30{M 2:1 (1025)} Pelvis, long bones of lower and upper extremities Characteristic Radiographic Feature: Periosteal reaction on bone surface gives classic “onion-
skin” appearance
Fibrosarcoma, MFH, spindle cell
sarcoma
40–70 Knee, hip and shoulder regions, pelvis
Malignant giant cell tumor 20–60 M 3:1 Knee region, pelvis, shoulder region High-grade sarcoma arising in GCT; classic GCT may rarely metastasize
Chordoma 30–80 Sacrococcygeal, skull base, vertebrae May rarely dedifferentiate
ABC aneurysmal bone cyst,
FD fibrous dysplasia,
GCT giant cell tumor,
MFH malignant fibrous histiocytoma,
PNET primitive neuroectodermal tumor

4. Age group Most common benign lesions Most common malignant tumors
0 - 10 simple bone cyst
eosinophilic granuloma
Ewing's sarcoma
leukemic involvement
metastatic
neuroblastoma
10-20 non-ossifying fibroma
fibrous dysplasia
simple bone cyst
aneurysmal bone cyst
osteochondroma (exostosis)
osteoid osteoma
osteoblastoma
chondroblastoma
chondromyxoid fibroma
osteosarcoma,
Ewing's sarcoma,
adamantinoma
20-40 enchondroma
giant cell tumor
chondrosarcoma
40 and above osteoma metastatic tumors
myeloma
leukemic involvement
chondrosarcoma
osteosarcoma (Paget'sassociated)
MFH
chordoma
SITE OF LONG BONE INVOLVEMENT
(Most primary bone tumors have favored sites within long bones; this may provide a clue to diagnosis).
1. Epiphyseal lesions:
o Chondroblastoma (Ch) and Giant Cell Tumor (GCT) are almost invariably centered in the epiphysis.
o Chondroblastoma is a rare tumor seen in children and adolescents with open growth plates. GCT is the most common tumor of epiphyses in skeletally mature individuals with closed growth plates. GCT often
shows metaphyseal extension.
2. Metaphyseal intramedullary lesions:
o Osteosarcoma is usually centered in the metaphysis.
o Chondrosarcoma and fibrosarcoma often present as metaphyseal lesions. Osteoblastoma, enchondroma, fibrous dysplasia, simple bone cyst, and aneurysmal bone cyst are common in this location.
3. Metaphyseal lesions centered in the cortex:
o Classic location for a non-ossifying fibroma (NOF).
o Also, a common site for osteoid osteoma.
4. Metaphyseal exostosis:
o Osteochondroma
5. Diaphyseal intramedullary lesions:
o Favored location for Ewing's sarcoma, lymphoma, myeloma.
o Common for fibrous dysplasia and enchondroma.
6. Diaphyseal lesions centered in the cortex:
o Adamantinoma, osteoid osteom

5. PATTERNS OF GROWTH and BONE DESTRUCTION
o Benign and non-growing (or extremely slowly growing) lesions are well circumscribed and show geographic pattern of bone destruction with a sclerotic rim. Geographic pattern refers to a well defined area of lysis.
The sclerotic rim is more commonly seen in the weight-bearing bones and represents bone reaction to the lesion. Its presence means that the bone has been given sufficient time to react. Some authors say that the
sclerotic rim signifies benignancy to about 95%.
o If the lesion is growing more rapidly, it may still show a well-demarcated zone of bone destruction (geographic pattern), but it will lack a sclerotic rim. With continued growth, such lesions may show cortical
expansion. Expansile growth pattern is defined as visible widening of the affected portion of bone. In many cases, an interrupted periosteal rim will surround the expanded portion of bone. This pattern may be seen in
locally aggressive tumors and in low-grade malignancies.
o Rapidly growing lesions are poorly defined and may show aggressive, infiltrative patterns of bone destruction (permeative or "motheaten"). "Moth-eaten" pattern is defined as an ill-defined zone of multiple small
radiolucencies that may coalesce.
o Permeative pattern is characterized by numerous tiny radiolucencies in between the residual bone trabeculae. Due to the minute size of radiolucencies the lesion may be difficult to see and to delineate on the plain
film. Generally, the more rapidly growing a lesion, the more difficult it is to see on plain film. "Moth-eaten" and permeative patterns are indicative of destruction involving both medullary and cortical bone. They are
seen in high-grade malignant neoplasms and in osteomyelitis.
TYPES OF PERIOSTEAL REACTION
The periosteum responds to traumatic stimuli or pressure from an underlying growing tumor by depositing new bone. The radiographic appearances of this response reflect the degree of aggressiveness of the tumor.
o Slow-growing tumors provoke focal cortical thickening (solid periosteal reaction, or "buttress")
o Rapidly growing lesions penetrate through the cortex causing separation of the periosteum and formation of lamellated new bone. If the periosteum elevates to a significant degree, it can break forming an acute angle
(Codman's triangle). This is seen in malignant bone tumors and in some other rapidly growing lesions such as aneurysmal bone cyst, or in reactive processes (osteomyelitis, and subperiosteal hematoma). Codman's
triangle is usually free of tumor unless infiltrated through its open end or by transcortical growth.
o Other types of periosteal reaction in response to a rapidly growing lesion include "onion-skinning" and spiculated "hair-on-end" types.
PATTERNS OF MATRIX MINERALIZATION
Mineralization patterns (calcification or ossification) are helpful in identification of bone producing and cartilage producing tumors.
o Osteoid: Malignant osteoid can be recognized radiologically as cloudlike or ill-defined amorphous densities with haphazard mineralization. This pattern is seen in osteosarcoma. Mature osteoid, or organized bone,
shows more orderly, trabecular pattern of ossification. This is characteristic of the benign bone-forming lesions such as osteoblastoma.
o Chondroid: Radiologically, it is usually easier to recognize cartilage as opposed to osteoid by the presence of focal stippled or flocculent densities, or in lobulated areas as rings or arcs of calcifications. They are best
demonstrated by CT. Whatever the pattern, it only suggests the histologic nature of the tissue (cartilage) but does not reliably differentiate between benign and malignant processes.