Enchondroma

Introduction

A benign chondrogenic lesion caused by an abnormality of chondroblast function in the physis chondroblasts escape the physis and proliferate in metaphysis  2nd most common benign cartilage lesion (osteochondroma is most common) Age & location age range is 10-60 years occurs in medullary cavity in diaphysis or metaphysis hand is most common location (60%) presentation as pathological fractures common other locations include the femur (20%) and proximal humerus (10%) Include solitary enchondroma 1% chance of malignant transformation (chondrosarcoma) Ollier's disease (multipe enchondromatosis)  no genetic predisposition has been identified multiple enchondromas in long bone diaphysis 10-30% chance of malignant transformation into chondrosarcoma however associated with high rate of both skeletal and non-skeletal malignancies involved bones are dysplastic Maffucci's syndrome no genetic predisposition has been identified multiple enchondromas and soft-tissue angiomas 100% chance of malignant transformation into chondrosarcoma  increased risk of visceral malignancies (astrocytoma, GI malignancy)

Symptoms

Presentation most are asymptomatic  often present as pathologic fx of the hand but asymptomatic in foot Physical exam enchondroma may disrupt the growth plate and lead to shortening and angular deformities

Imaging

Radiograph "pop-corn" mineralization (calcification), stippled ringsin diaphyseal or metaphyseal medullary cavity  occasionally may have purly lytic appearance (especially in hand)  Bone scan may be helpful and is usually minimally warm MRI may show steak of cartilage or "sled runner tracks"

Histology

Classic characteristics include hypocellular with bland hyaline cartilage (blue balls of cartilage)    lesions in hand are more hypercellular and even display some worrisome histologic characteristics small chondroid cells in lacunar spaces

Differential

Must differentiate from a bone infarct ("smoke-up-chimney" appearance)

Treatment

Nonoperative observation treatment for most enchondromas  watch with serial xrays for interval growth (obtain xrays at 3 months and 1 year from time of presentation) Operative curettage and bone grafting indications lesion that shows any change on serial xrays hand fractures after fracture has first been allowed to heal with imobilization Ollier's disease and Maffucci's treat deformity with diaphysectomy watch lesions carefully for malignant transformation