Chondromyxoid fibroma (CMF) is a benign cartilage tumor that also has
myxoid and fibrous elements. It is extremely rare and accounts for less that 1% of all bone tumors.i CMF is found most
often in the metaphysis around the knee in the proximal tibia, proximal fibula, or distal femur. It presents in the
second to third decade and has a male to female ratio of 2 to 1. The clinical presentation is usually chronic pain,
swelling and possibly a palpable soft tissue mass or restriction of movement. Only 5% of patients with CMF present
with a pathological fracture.”
Radiological
findings demonstrate an eccentrically placed Iytic lesion with well defined margins in the metaphysis of the lower
extremity. The lesion usually has a sclerotic margin of bone and a lobulated contour. Ridges and grooves that appear
in the margins secondary to scalloping falsely appear to be trabeculae. CT helps define cortical integrity and
confirms that there is no mineralization of the matrix, unlike other cartilage tumors. CMF has the same appearance on
MRI as other cartilage tumors which is decreased signal on T 1 weighted images and increased signal on T2 weighted
images. MRI is helpful in preoperative planning and staging. The radiologic differential diagnosis includes giant
cell tumor, chondro_myxoidfibroma bone cyst, unicameral bone cyst, chondroblastoma and fibrous dysplasia.
CMF
resembles fibrocartilage grossly. It has a sharp border often with an outer surface of thin bone or periosteum. The
glistening grayish white lesion is firm and lobulated. It may also have small cystic foci or areas of
hemorrhage.
Histologically,
CMF appears very similar to chondrosarcoma. They are so close in histology that often radiology helps to make the
final diagnosis. The predominant features of CMF are the zonal architecture and lobular pattern. Nodules of cartilage
are found in between fibromyxoid areas. In some fields the loose myxoid dominates and in other the dense chondroid
dominates. The chondrocytes are plump to spindly in shape and have indistinct cell borders in sparsely cellular
lobules of myxoid or chondroid matrix. There are also more cellular zones of the tumor with some giant cells at the
edges. The sharp borders of each lobule and the lesion itself help to differentiate it from
chondrosarcoma.
Treatment
of CMF is en bloc excision. Recurrences after curettage are common.
References
Giudici,
M. et al, Cartilaginous Rone Tumors, Radiologic Clinics of North America, 31(2):237-259, March 1993. UGiudici et
al.
Bulloughs,
Peter, Orthopedic Pathologv (third edition), Times Mirror International Publishers Limited, London,
1997.
Huvos, Andrew, Bone Tumors:Diagnosis. Treatment and Prognosis, W.B. Saunders, Co.,
1991.
Adapted, with permission from bonetumor.com By Henry DeGroot III, M.D.
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