Surface chondromyxoid fibroma of the distal ulna: unusual tumor, site, and age

Chondromyxoid fibroma (CMF) is a rare benign cartilage congener tumor comprising less than 1 % of primary bone tumors. Although the age range is wide, it is most commonly seen in the second and third decades. The most frequent location of CMF is in the long tubular bones of the lower extremities, particularly the proximal tibia and distal femur. Although the majority of chondromyxoid fibromas present as intramedullary tumors, a subgroup of chondromyxoid fibromas arising as surface lesions of the bone has recently been described. These are associated with an older mean age and an increased incidence of matrix calcifications. Chondromyxoid fibromas are rare in the distal ulna. We report a CMF presenting as a surface lesion of the distal metaphysis of the left ulna in a 41-year-old woman. We reviewed the literature on chondromyxoid fibromas involving the ulna and found that out of 22 cases, 1 was in the distal ulna, 13 in the proximal ulna, and in the remaining 8 the ulnar sites were unspecified. No case of chondromyxoid fibroma in the published literature had been designated as a surface lesion. Our own unpublished data include 70 chondromyxoid fibromas, 4 of which are in the ulna. Two of these are in the distal portion.