Radiographic and Pathologic Characteristics of Common Bone Neoplasms

Nick Luem Diagnostic Radiology June 24, 2007

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Classification of the more common bone tumors

Benign Neoplasms – Osteochondroma – Chondroma – Giant Cell Tumor – Aneurysmal Bone Cyst  Malignant Neoplasms – Osteogenic sarcoma – Chondrosarcoma – Ewing’s sarcoma

Osteochondroma

     Also known as exostosis Children and teenagers most affected, Men >> Women Clinically appear as slow growing masses, painful if impinging on nerve tissue Solitary or multiple Multiple Hereditary Exostosis  autosomal dominant disease with inactivation of both copies of EXT gene in growth plate chondrocytes

Osteochondroma

     Benign projection of bone with cartilaginous cap Occurs in epiphyseal plate and grows laterally Exhibits cortex and medullary portion May convert to malignancy if cartilage cap becomes thicker and contains disorganized calcifications Conversion to sarcoma rare (<1%) but higher in patients with hereditary syndrome

Osteochondroma

 Ultrasound safe and inexpensive way to evaluate thickness of cartilaginous capsule  Develops in bones of endochondral origin and arises from the metaphysis near the growth plate of long tubular bones.

 Occasionally develops from bones of the pelvis, scapula and ribs  MRI method of choice to evaluate thicknesss of cartilaginous cap to rule out malignant conversion

- Radiograph can demonstrate that cortex of osteochondroma blends with cortex of normal bone - Long axis of tumor usually runs parallel to parent bone and points away from parent joint

Osteochondroma: Disorganized growth plate with endochondral ossification Newly made bone forms inner portion of head and stalk Medullary cavity of osteochondroma and bone are continuous

Chondroma

       Slow-growing tumor of hyaline cartilage Enchondromas  arise within medullary cavity Juxtacortical chondroma  arise on bone surface Destroys normal bone by erupting as mixture of calcified and uncalcified hyaline cartilage Occur in children and young adults Enchondromas usually solitary Favor the metaphyseal region of tubular bones such as the small bones of the hand and feet

Chondroma

     Most asymptomatic and found incidentally Occasionally cause pathologic fractures Ollier disease  enchondromas syndrome of multiple Maffuci syndrome  enchondromatosis associated with soft tissue hemagiomas May recur if incompletely excised

-Radiographic findings of enchondromas include a stippled ringlike or arclike calcifications within the lucent matrix -Cartilage nodules can form well-circumscribed oval lucencies surrounded by thin rim of radiodense bone, the “O ring sign” -T2-weighted MR images show lesion with lobulated borders from endosteal scalloping and containing focal areas of high signal intensity -Nuclear medicine scans usually negative in enchondromas, ruling out the possibility of malignancy

Nodules of cartilage that are well circumscribed with a hyaline matrix -The neoplastic chondrocytes in the lacunae are cytologically benign -Cartilage at the periphery of the nodule undergoes endochondral ossification

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Giant Cell Tumor

Name derives from abundant multinucleated osteoclast-type giant cells  Uncommon but locally aggressive tumor. Usually arises in patients in their twenties to forties.

 Giant cell tumors in adults involve both epiphyses and metaphyses, but in adolescents are confined proximally by the growth plate and are limited to the metaphysis  Majority occur in the distal femur and proximal tibia but any bone may be involved  May cause arthritic symptoms in patients or lead to pathologic fractures

Giant Cell Tumor

Large red to brown tumors that undergo cystic degeneration

Giant Cell Tumor

     Conservative surgery, such as curettage, associated with 40% to 60% recurrence rate Up to 4% metastasize to the lungs Some lesions can be pre-malignant or malignant MRI used to determine intraarticular extension, soft tissue involvement and bone marrow changes Diagnostic accuracy high when MR images and X-ray images are combined

 Characteristic radiographic appearance of Giant Cell Tumor: multiple large bubbles separated by thin strips of bone

Giant Cell Tumor

Tumor is composed of uniform oval mononuclear cells with indistinct membranes and appear to grow in a syncytium Scattered within this background are numerous osteoclast-type giant cells Necrosis, hemorrhage, hemosiderin deposition and reactive bone formation are frequent secondary features

Aneurysmal Bone Cyst

 Not a true neoplasm or cyst  Numerous blood filled arteriovenous communications  Thought to be secondary to trauma  Often mistaken for malignant tumor on plain radiograph

Aneurysmal Bone Cyst

 CT can show the lobulations of the lesion  MRI shows internal loculation and fluid levels that produce low signal on T2 weighted images  T1-weighted images show cyst with a low to intermediate signal intensity. Signal intensity increases if acute hemorrhage present

Aneurysmal Bone Cyst

 Expansile, eccentric, cystlike lesion that causes pronounced ballooning of thinned cortex in long bones  Cystic lesion has multiple, fine internal septa

Aneurysmal Bone Cyst

Microscopically, the ABC has cystic spaces filled with blood. The fibrous septa have immature woven bone trabeculae as well as capillaries hemosiderin-laden macrophages, fibroblasts, and giant cells.

Malignant neoplasms

 Osteosarcoma  Chondrosarcoma  Ewing’s Sarcoma

Osteosarcoma

    Malignant mesenchymal tumor in which cancerous cells produce bone matrix Accounts for approximately 20% of primary bone cancers Bimodal age distribution; 75% occur in patients <20 years. Second peak occurs in older adults who have known conditions associated with the development of osteosarcoma (Paget disease, bone infarcts, prior irradiation) Metaphyseal region of long bones common site, roughly 60% occur about the knee

Osteosarcoma

 Patient with hereditary retinoblastomas have up to 1000 times greater risk of developing osteosarcoma  Attributed to germ line mutations in RB gene  Abnormalities in other genes that regulate cell cycling implicated (CDK4, p16, INK4A, CYCLIN D1, MDM2)  Typically present as painful and progressively enlarging masses. At time of diagnosis, aprox. 10%-20% of patients have metastates to the lungs

Osteosarcoma

Reactive periosteal bone forms when tumor breaks through cortex This leaves a triangular shadow between the cortex and raised ends of periosteum known radiographically as “Codman triangle”

Osteosarcoma

Tan-white tumor fills most of the medullary cavity of the metaphysis and proximal diaphysis The tumor infiltrates through the cortex, lifts the periosteum and forms soft tissue masses on the side of the bone Several subtypes are recognized and grouped by location, degree of differentiation, multicentricity and histologic variance

Osteosarcoma

Coarse, lacelike pattern of neoplastic bone formed by anaplastic malignant tumor cells. Bone may be deposited in large sheets of primitive trabeculae Cartilage and fibrous tissue may be present in varying amounts. Vascular invasion usually conspicuous and spontaneous necrosis is common

Chondrosarcoma

Chondrosarcomas produce neoplastic cartilage Second most common malignant matrix-producing tumor of bone Subclassified by: Site  intramedullary, juxtacortical Histology  conventional, clear cell, dedifferentiated, mesenchymal variant

Patients usually >40 yrs of age Men affected twice as frequently as women Commonly arise in central portions of skeleton: pelvis,shoulder and ribs. Clear cell variant originates in the epiphyses of long tubular bones Often contain punctate or amorphous calcification within its cartilaginous matrix Endosteal scalloping and cortical destruction seen radiographically The more radiolucent the tumor, the greater likelihood of a higher grade

Chondrosarcoma

Tumors vary in degree of cellularity, cytologic atypia and mitotic activity Low grade: mild hypercellularity, plump vesicular nuclei with small nucleoli, and sparse mitotic figures High grade: extreme pleomorphism with bizarre tumor giant cells and mitoses

Ewing’s Sarcoma

    Small round cell tumor of bone Accounts for 6%-10% of primary malignant bone tumors Most patients between 10 to 15 years old; youngest average age at presentation of all bone tumors Treatment includes chemotherapy and surgical excision. At least 50% are cured long term

Classic radiographic appearance: Ill-defined permeative area of bone destruction Involves large central portion of the shaft of a long bone Ewing sarcoma typically arises in the medullary cavity and invades the cortex and periosteum Associated with a fusiform layered periosteal reaction parallel to the shaft, the classic “Onionskin appearance”

Tumor composed of sheets of uniform,small, round cells that are slightly larger than lymphocytes with scant cytoplasm Generally little stroma and necrosis maybe prominent Relatively few mitotic figures in relation to the dense cellularity of the tumor

References

 Robbins and Cotran, Pathologic Basis of Disease 7 th Edition. Elsevier Saunders, Philadelphia, PA  Eisenberg, Comprehensive Radiographic Pathology 4 th Edition. Mosby, St. Louis, MO  Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging 4 th Edition.