What is an enchondroma?

What is an Enchondroma

An enchondroma is a benign, cartilaginous neoplasm that arises from the medullary cavity of bones and causes bone expansion, typically growing to sizes up to 3 cm and usually not causing pain. 1

Basic Characteristics

• Enchondromas are benign mature hyaline cartilaginous tumors located within the medullary space of bones. 2
• They constitute 3-10% of all bone tumors and 12-24% of benign bone tumors. 3
• These lesions originate from growth plate cartilage that proliferates to form the enchondroma. 3

Common Locations

• Most commonly occur in the small bones of the hands and feet (up to 90% in the hand). 4
• In the hand, the proximal phalanx is most frequently affected (44.8%), with no particular finger preference except the thumb which is affected less commonly (9.8%). 4
• Less common sites include the distal femur and proximal humerus. 3
• Can occur in long bones where they are typically metaphyseal in location. 3

Clinical Presentation

• Most solitary enchondromas are asymptomatic and discovered incidentally. 5
• When symptomatic, patients present with pain and swelling (51.7% of cases) or pathological fracture (25% of cases). 4
• Asymptomatic lesions without fracture can also prompt evaluation due to visible enlargement. 2
• Rare presentations include clubbing and longitudinal erythronychia in toe lesions. 5

Radiological Features

• Radiographs show a localized, radiolucent lytic bone defect usually with punctuate calcifications. 3
• Lesions are central or eccentric with metaphyseal involvement most common in long bones. 3
• Contrast-enhanced MRI can help differentiate benign enchondroma from atypical cartilaginous tumor/grade I chondrosarcoma. 1

Multiple Enchondromas (Enchondromatoses)

• When multiple enchondromas occur, this is termed enchondromatosis, with Ollier disease being the most common subtype (prevalence 1:100,000). 1
• Ollier disease typically presents in early life (median age 4.8-11 years) with enchondromas in short and long tubular bones of the limbs. 1
• Maffucci syndrome combines multiple enchondromas with benign vascular overgrowths. 1
• In 80% of enchondromatosis cases, there are somatic variants in IDH1 (at p.Arg132) or IDH2 (at p.Arg172Ser). 1

Malignant Transformation Risk

• Solitary enchondromas have very low malignant transformation risk (<5% recurrence suggests malignancy). 3
• In enchondromatosis (Ollier disease and Maffucci syndrome), malignant transformation to chondrosarcoma occurs in approximately 30% of patients. 1
• Transformation typically occurs at median age 30-52 years but can occur as young as 10 years. 1
• High-risk sites for transformation include femur, tibia, humerus, pelvis, and scapula. 1
• Pain at the site of a cartilaginous lesion may indicate malignancy, though asymptomatic chondrosarcomas are also reported. 1

Management Approach

• Asymptomatic solitary enchondromas can be managed conservatively with serial radiological follow-ups every 6 months. 3, 4
• Symptomatic cases require operative management with curettage and bone grafting. 3
• Standard treatment is accurate extirpation of the tumor with subsequent filling of the defect with cancellous bone. 4
• For enchondromatosis, physical examination should occur every 6-12 months from birth, with plain radiographs of known lesions every 2-3 years. 1
• Lesions >5-6 cm or in the pelvis/scapula warrant annual dedicated MRI surveillance. 1

Prognosis

• Recurrence rate after treatment is very low (<5%) in solitary enchondromas. 3
• 84.2% of patients achieve "very good" or "good" functional long-term outcomes after treatment. 4
• In enchondromatosis with secondary chondrosarcoma, prognosis is generally good with 5-year survival >90%, as the grade is often low and tumors rarely metastasize. 1

Important Clinical Pitfalls

• Pain is not a reliable indicator—some chondrosarcomas are asymptomatic while some benign lesions cause pain. 1
• Increasing tumor size should prompt targeted MRI and consideration of biopsy regardless of symptoms. 1
• Histopathological examination is essential for definitive diagnosis and to differentiate from malignant chondrosarcoma. 2, 5