Chondroma

Chondroma is a benign cartilage-forming tumor. Types are enchondroma (inside the medullary cavity, the most common), periosteal (juxtacortical) chondroma and soft tissue chondroma. Enchondromas are found incidentally in about 3% of knee MRI scans. About 40 to 50% occur in the small bones of the hand (proximal phalanges and metacarpals), and the remainder in the femur, humerus and tibia. Peak age is 10 to 40 years.

Multiple enchondromatosis

• Ollier disease: multiple enchondromas, often unilateral, with limb deformity and shortening
• Maffucci syndrome: enchondromas with soft tissue hemangiomas

IDH1 and IDH2 mutations are found in most. A solitary enchondroma of the hand has a malignant transformation risk under 1%, long bone and pelvic tumors carry 1 to 5%, Ollier disease 25 to 50% and Maffucci syndrome up to about 50% (with other malignancies such as glioma and ovarian tumors). Complications: pathologic fracture, deformity, and transformation to chondrosarcoma.

• Usually asymptomatic and discovered by chance
• Painless swelling of a finger, or pathologic fracture after minor trauma
• Ollier disease: bone deformity, limb length discrepancy and growth disturbance
• Features suggesting malignant change: deep pain at rest or at night (not explained by fracture), growth after skeletal maturity, a new soft tissue mass, and cortical destruction

1. Radiographs: a well-defined lytic lesion in the medullary cavity with stippled, ring or arc calcification, with mild endosteal scalloping. Hand lesions often lack calcification.
2. MRI for equivocal lesions: lobulated, high signal on T2 with peripheral and septal enhancement. Features of concern are endosteal scalloping over two thirds of cortical thickness, cortical breach, a soft tissue mass, a periosteal reaction and a cartilage cap over 2 cm.
3. Bone scan is of limited value. Increased uptake alone does not indicate malignancy.
4. Biopsy only when imaging is concerning. Histology: hypocellular hyaline cartilage with bland nuclei.

Differentials: atypical cartilaginous tumor and grade 1 chondrosarcoma, bone infarct, fibrous dysplasia, chondroblastoma, bone cyst, osteochondroma.

• Asymptomatic solitary enchondroma of a long bone: observation with radiographs or MRI at 6 and 12 months, then every 1 to 2 years for several years. Discharge when stable.
• Hand enchondroma with a weakened cortex or symptoms: extended curettage with autologous or synthetic bone graft, or cement when needed. Pathologic fracture is allowed to heal for 4 to 6 weeks, then curettage and grafting.
• Periosteal chondroma: marginal excision for symptoms.
• Symptomatic long bone lesions without features of malignancy: extended curettage with cryotherapy or phenol and grafting, with internal fixation for a large defect.
• Suspected chondrosarcoma (pain, growth, cortical destruction): needle biopsy and wide resection when confirmed.
• Ollier and Maffucci: whole-body MRI at diagnosis and every 1 to 2 years, corrective osteotomy and limb lengthening for deformity, and urgent evaluation of any new pain or growth. Screen for other tumors in Maffucci syndrome (brain MRI, abdominal imaging).
• Perioperative: cefazolin 2 g IV before incision (children 30 mg/kg), and analgesia with paracetamol 1 g orally every 6 hours.

Follow-up at 2 and 6 weeks after surgery, then yearly. Counsel patients on reporting night pain or growth.