History: 35 year old male with hand pain.
This is a classic appearance of an enchondroma in a phalanx on radiographs. An enchondroma is a benign cartilaginous tumor that arises from the medullary space of the bone. Enchondromas are the second most common benign tumor of bones (after osteochondroma) and most common benign tumor of small tubular bones, as seen here in the fourth proximal phalanx of the hand.
On MRI, enchondromas are characteristically lobulated with homogeneous hyperintense signal on fluid sensitive sequences, typical of benign cartilaginous lesions. Ideally, contrast is required to definitively distinguish between enchondromas and low grade chondrosarcomas, as some enchondromas can degenerate into chondrosarcomas. This is shown radiographically by excessive endosteal scalloping, and on MRI with contrast as peripheral puddling of contrast within the lesion. Another distinguishing factor is pain, indicating likely chondrosarcoma. Read more about other distinguishing findings here.
See an Enchondroma of the tibia on MRI here.
See the differential diagnosis for lytic bone lesions here.