Enchondroma

Tumur template based on A Clinical Guide to Primary Bone Tumors. Levesque et al.

Tumor biology and incidence

Enchondromas are benign intramedullary cartilage lesions which occur primarily in long bones.  They are usually asymptomatic, consisting of hyaline cartilage.  Their etiology is unknown, however are believed to be the result of incomplete endochondral ossification.  It is thought rests of physeal cartlilage become entrapped in the metaphysis of growing bones.  They are the second most common type of benign cartilage lesion, occuring most frequently in small bones of hand, femur, and humerus, but rarely occur in pelvis or shoulder girdle.  Approximately 1% of solitary lesions can progress to malignancy. 

Age

ages 20-50

Gender

M=F

Presentation

Usually asymptomatic, found on xray as incidental finding.   

Physical findings

Usually asymptomatic.  If painful, are usually associated with other regional pathology or diagnosis. 

Plain films

Appear as mineralized long, oval intamedullary lesions, centrally located in metaphysis or metadiaphysis.  The mineralizations are described as punctate rings and arc patterns.  They have intact an intact cortex without any pariosteal reactionor cortical thickening, uless they are in the setting of a pathologic fracture.  In the small bones of hands and feet there is often endosteal scalloping and well demarcated lesions, extending to the ends of bones. 

Site
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Size

Common sites involve the metaphysis or metadiaphysis of the bones of hand, humerus femur and foot.

Tumor effect on bone

Enchondromas are typically < 6 cm, and can sometimes have endosteal scalloping.  However periosteal reaction or cortical thickening is rare.  Cortical thinning can occur in the small bones of the hand. 

Bone response to tumor

Cortical thinning can occur in the small bones of the hand.

Matrix

Enchondromas are benign intramedullary lesions consisting of hyaline cartilage with rings and arcs of mineralization.

Cortex

Endosteal scalloping and cortical thinning is more evident in the hand.  The long bones can be characterized by expansile lesions with no cortical thickening or thinning. 

Soft tissue mass

Cortex is not violated.  Soft tissue masses suggest a malignant process.

Bone scan

Variable uptake in the skelatally immature as the enchondromas grow. 

CT Scan

Can be used to evaluate extent of mineralization and endosteal scalloping, which can help distinguish enchondromas from chondrosarcomas.

MRI

An MRI is useful for evaluating the extent of extension within the marrow and can better demonstrate the lobular nature of the lesion.  The mineralizations can be seen as dark areas on T1 and T2 series.

Differential Diagnosis

Bone infarct, Enostosis, and chondrosarcoma.  Signs worisome of chondrosarcoma are: pain, soft tissue extension, size > 5 cm, periosteal reaction, cortical destruction, medullary fill > 90%)

Natural history

Growth of the lesion is rare after skelatal maturity, and malignant transformation can occur in 1% of solitary lesions.  However, in patients with Ollier's disease (multiple enchodromas) have significant risk of malignant transformation up to 30%.  Maffucci's syndrome (multiple enchondromas and associated soft tissue lesions, most commonly hemangiomas) has been described to undergo malignant transformation in up to 100% of cases.

Pathology

Well circumsribed lesion of hyaline cartilage lobules, histologically hypocellular.  It can be difficult to distinguish enchondroma from low grade chondrosarcoma on histology alone.   

Diagnosis and treatment

If a lesion is thought to be an enchondroma, surgical intervention is rarely indicated.  These lesions are usually followed conservatively with radiographs to follow for changes in characteristic or size.  Biopsies can be difficult to differentiate between enchondromas and low grade chondrosarcomas.  Therefor, the distinction is usually based on clinical correlation and radiographic appearance.  Enlarging or painful lesions can be treated with curretage and bone graft.  The use of adjuvent therapy such as phenol or liquid nitrogen is controversial.  THe recurrence rate for curretage of benign lesions is less than 5%.  If the clinical or radiographic picture suggest a more aggressive lesion a biopsy may be warrented.  However usually in these cases the lesion is removed surgically irregardless.   A potential high grade lesion should be treated with wide excision. 

Complications

Up to 5% of benign lesion can recur with curretage and bone graft. Surgical treatment of pathologic fractures of the hand are generally delayed til the fracture is healed and then can be curretaged.  Impending fractures can be treated prophylactically with curretage and bone graft, and if neccessary, internal fixation or cement.

Recommended Reading

Oncology and Basic Science. Ed: Timothy A. Damron. Orthopedic Surgery Essentials Series, 576pp, Philadelphia, PA, Lippincott Williams & Wilkins, 2007. 

Orthopaedic Knowledge Update: Musculoskeletal Tumors 2. Herbert S. Schwartz, MD, Editor. American Academy of Orthopaedic Surgeons, Rosemont Il, 2007

 Flemming DJ, Murphey MD: Enchondroma and Chondrosarcoma. Semin Musculo Radiol 2000;4:59-71.