1. Describe the primary lesion.
There is an intramedullary lesion located within the proximal metaphysis and diaphysis of the humerus. It appears predominantly sclerotic with irregular margins. The cortex appears intact and there is no evidence of periosteal reaction or soft tissue mass. There is no pathologic fracture.
2. Which categories of disease would apply to this lesion?
The categories of disease include Congenital, Arthritis, Trauma, Blood/vascular, Infection, Tumor, Endocrine/metabolic, and Soft tissue (CATBITES). The most likely categories which would apply to this lesion include a vascular lesion and neoplasm.
3. List your differential diagnosis.
Top two differentials would be enchondroma and avascular necrosis. Also consider a low grade chondrosarcoma which could be radiographically similar to an enchondroma. Fibrous dysplasia may also be considered, although ideally it would have a more homogeneous ground-glass opaque appearance.
DIAGNOSIS: Enchondroma
DISCUSSION
Enchondromas are a benign cartilaginous tumor of bone, made up of lobules of hyaline cartilag and represent the second most common benign tumor of bone. Up to 50% occur in the short bones of the hands, 25% occur in the long bones with the femur and humeurs being most common. In long bones, as seen in this case, the lesion is metaphyseal and/or diaphyseal in location.
Radiographically the lesions may appears lytic. Up to 95% show lobulated "popcorn-like" or fleck-like calcifications to a varying degee. The lesions may be slightly expansile in the short bones of the hands, but the cortex should remain intact and there is no evidence of soft tissue mass. The presence of cortical violation should lead you to suspect fracture or malignant degeneration. The incidence of malignant degeneration to a low grade chondrosarcoma are low.
MRI is not typically required to make the diagnosis. In cases where there is an indeterminate radiographic diagnosis or concern for malignant degeneration then MRI may be useful for evaluation of the lesion. On MRI enchondromas appear low on T1-weigthed images, similar to muscle, and bright on T2 and STIR-weighted sequences. Calcifications will appear low on both T1 and T2 weighting.
The MRI appearance of the lesion, same patient as above:
There is an intramedullary lesion located within the proximal metaphysis and diaphysis of the humerus. It appears predominantly sclerotic with irregular margins. The cortex appears intact and there is no evidence of periosteal reaction or soft tissue mass. There is no pathologic fracture.
2. Which categories of disease would apply to this lesion?
The categories of disease include Congenital, Arthritis, Trauma, Blood/vascular, Infection, Tumor, Endocrine/metabolic, and Soft tissue (CATBITES). The most likely categories which would apply to this lesion include a vascular lesion and neoplasm.
3. List your differential diagnosis.
Top two differentials would be enchondroma and avascular necrosis. Also consider a low grade chondrosarcoma which could be radiographically similar to an enchondroma. Fibrous dysplasia may also be considered, although ideally it would have a more homogeneous ground-glass opaque appearance.
DIAGNOSIS: Enchondroma
DISCUSSION
Enchondromas are a benign cartilaginous tumor of bone, made up of lobules of hyaline cartilag and represent the second most common benign tumor of bone. Up to 50% occur in the short bones of the hands, 25% occur in the long bones with the femur and humeurs being most common. In long bones, as seen in this case, the lesion is metaphyseal and/or diaphyseal in location.
Radiographically the lesions may appears lytic. Up to 95% show lobulated "popcorn-like" or fleck-like calcifications to a varying degee. The lesions may be slightly expansile in the short bones of the hands, but the cortex should remain intact and there is no evidence of soft tissue mass. The presence of cortical violation should lead you to suspect fracture or malignant degeneration. The incidence of malignant degeneration to a low grade chondrosarcoma are low.
MRI is not typically required to make the diagnosis. In cases where there is an indeterminate radiographic diagnosis or concern for malignant degeneration then MRI may be useful for evaluation of the lesion. On MRI enchondromas appear low on T1-weigthed images, similar to muscle, and bright on T2 and STIR-weighted sequences. Calcifications will appear low on both T1 and T2 weighting.
The MRI appearance of the lesion, same patient as above:
The lesion demonstrates the lobules of cartilage seen as the high T2W signal. The ares of low signal correspond to the calcification on the x-ray study. There is variable enhancement with gadolinium contrast. The presence of enhancement in and of itself is not an indicator for malignant degeneration. Studies in recent years, however, have shown that rapid early contrast enhancement within a cartilaginous lesion shows potential as having predictive value for identifying low grade chondrosarcomas.
TREATMENT AND PROGNOSIS
Since most lesions are asymptomatic, they are usually an asymptomatic finding. Enchondromas associated with pain are typically the result of fracture involving a lesion in the tubular bones of the hands and feet. Those may be treated with fixation to speed healing. On occasion curettage of the enchondroma and bone grafting may be performed. New pain without evidence of a fracture and an interval change in the radiographic appearance such as periosteal reaction, increased size, or decreased calcification within the lesion should raise suspicion for malignant degeneration and warrant futher clinical follow up.
TREATMENT AND PROGNOSIS
Since most lesions are asymptomatic, they are usually an asymptomatic finding. Enchondromas associated with pain are typically the result of fracture involving a lesion in the tubular bones of the hands and feet. Those may be treated with fixation to speed healing. On occasion curettage of the enchondroma and bone grafting may be performed. New pain without evidence of a fracture and an interval change in the radiographic appearance such as periosteal reaction, increased size, or decreased calcification within the lesion should raise suspicion for malignant degeneration and warrant futher clinical follow up.