Chondromyxoid fibroma of the distal phalanx of the great toe: a tumor with unusual histological findings.

Chondromyxoid fibroma (CMF) rarely arises in the distal phalanx of the foot and less than 20 cases have been reported in the literature. It has also been known to show a wide spectrum of histology mimicking other primary bone tumors. An unusual case of CMF arising in the distal phalanx of the left great toe is reported because of its unique anatomic site of origin and histology. A 53-year-old female presented with a slow growing, painful great toe of the left foot which she had had for 3 years. She had first noticed the mass 25 years ago. On admission, plain X-ray revealed an osteolytic mass with a sclerotic margin expanding to the distal phalanx of the great toe. Interestingly, the lesion was microscopically composed of hypercellular chondromyxoid lobules separated by hypocellular fibrous tissue, which is in contrast to the typical histology of CMF. In addition, the lesion showed an aggregate of tumor cells with pleomorphic multinucleate or giant nuclei within the chondromyxoid matrix, which were not similar to the osteoclast-like type. Perhaps these unusual histological findings may be associated with its long duration and presenting location.