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Enchondroma in the left proximal humerus

Enchondromas are benign cartilaginous neoplasms that originate in the medullary canal of tubular bones. Twenty percent of enchondromas occur in long bones (femur and humerus), 40-60% occur in the short bones of the hands and feet, with the remaining found in the rib (at the cartilaginous end), sternum, and skull base. Flat bones are rarely affected. Enchondromas are slow growing, composed of mature hyaline cartilage. Males and females are equally affected. When enchondromas occur in multiple long bones, the condition is called multiple enchondromatosis or dyschondroplasia (Ollierís disease). Risk for malignant transformation is believed to be around 10-25%. Multiple enchondromatosis with soft tissue and visceral hemangiomas defined as Maffucci's syndrome are believed to be at far greater risk for malignant transformation than those with Ollier's disease.

x-ray demonstrate low grade cartilaginous lesion in proximal humerus which most likely represent enchondroma
x-ray demonstrate low grade cartilaginous lesion in proximal humerus which most likely represent enchondroma

CT guided biopsy demonstrates benign cartilaginous lesion - enchondroma
CT guided biopsy demonstrates benign cartilaginous lesion - enchondroma

Cor T1 (6 mo F/U)
Cor T1 (6 mo F/U)

Cor T2 Fat Sat  (6 mo F/U)
Cor T2 Fat Sat (6 mo F/U)

Ax T1 Fat Sat C  (6 mo F/U)
Ax T1 Fat Sat C (6 mo F/U)

History: 58 yo F patient was sent to oncologist because of pain and suspicious lesion in the left proximal humerus seen on outside MRI. Radiograph performed in our hospital demonstrated benign cartilaginous lesion which most likely represents enchondroma. Upon reviewing outside shoulder MRI and consultation with oncologist, we suggested a 6 month follow up MRI examination. The oncologist, because of the patient's symptoms, insisted on biopsy to exclude malignancy. Biopsy was negative for malignancy. Six mo follow up MRI of the lesion showed no interval change.

Enchondromas are benign cartilaginous neoplasms that originate in the medullary canal of tubular bones, believed to result from growth of residual benign cartilage rests displaced from the physis. They are often incidental findings, occurring in just under 2% of the population based on autopsy series. Twenty percent of enchondromas occur in long bones (femur and humerus), 40-60% occur in the short bones of the hands and feet, with rest found in the rib (at the cartilaginous end), sternum, and skull base. Flat bones are rarely affected.

Enchondromas are slow growing, composed of mature hyaline cartilage. Most are incidentally discovered. Males and females are equally affected. Infrequently they are symptomatic, causing soft tissue swelling and, less likely, pain at the lesion site. Pain can be a sign of pathologic fracture or malignant transformation. No treatment is required for asymptomatic lesions. When enchondromas occur in multiple long bones, the condition is called multiple enchondromatosis or dyschondroplasia (OllierÔŅĹs disease). Risk for malignant transformation is believed to be around 10-25%. Multiple enchondromatosis with soft tissue and visceral hemangiomas defined as Maffucci's syndrome are believed to be at far greater risk for malignant transformation than those with Ollier's disease.

Radiographically, enchondromas appear as geographic, mildly expansile, lytic lesions, which may lead to mild cortical thinning. The zone of transition is narrow, although it can be lobular. A cartilaginous matrix (rings and arcs) is often present, less often in lesions occurring in the hands and feet. There is no cortical breakthrough or host response in the absence of fracture. Enchondromas are usually monostotic, although multiple lesions can occur in the feet and hands.

On MR, they have typical signal characteristics of cartilaginous lesions with low signal on T1 and very high signal on T2 (due to high water and mucopolysaccharide content).
A small percentage of enchondromas will undergo malignant transformation (chondrosarcoma). The difficult diagnostic dilemma is distinguishing enchondroma from low-grade chondrosarcoma. The latter are usually larger, occur in less typical places (axial location), generally occur more proximal (epiphyseal location), may have deeper and more pronounced endosteal scalloping and may demonstrate destructive change. More importantly, local pain related to the lesion is always concerning for malignancy. The malignant transformation is usually a slow process, occurring over decades. It is more common in long bones than short.

Suggested reading:

Manaster BJ, Disler DG, May DA. Musculoskeletal imaging: the requisites. 2nd ed. 2002 Mosby, Inc. St. Louis. pp 37-43

Murphy M, Flemming D, Boyea S, Bojescul J, Sweet D, Temple H. Enchondroma vs chondrosarcoma in the appendicular skeleton: differentiating features. Radiographics 18:1213-1237, 1998.

Holtz P, Sundaram M: Radiologic case study. Enchondroma. Orthopedics 1995 May; 18(5):505, 505-10.
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