Subperiosteal Chondromyxoid Fibroma: A Report of Two Cases

Abstract

Chondromyxoid fibroma is a rare cartilage tumor that represents less than 1% of all bone tumors. When in a long bone, it is usually an intramedullary lesion that is eccentrically located in the metaphyseal region. Chondromyxoid fibroma may also have unusual presentations. These include intracortical lesions and subperiosteal lesions. There have been 14 reported cases of intracortical chondromyxoid fibroma, but there have been only four reports of subperiosteal lesions. A subperiosteal location, therefore, is extremely rare for a chondromyxoid fibroma. We present two new cases of subperiosteal chondromyxoid fibroma. Given its rarity, chondromyxoid fibroma is often not in the differential diagnosis of a painful, subperiosteal scalloped lesion in a long bone. Other entities such as periosteal chondroma, periosteal myxoma, subperiosteal ganglion cyst, or subperiosteal osteoid osteoma are more likely to be considered. Our cases illustrates that subperiosteal chondromyxoid fibroma, although rare, should be included in the differential diagnosis of a painful, radiographically inactive lytic lesion on the surface of a long bone.

INTRODUCTION

Chondromyxoid fibroma is a rare, benign cartilage tumor characterized by incomplete cartilage differentiation. It is the least common benign tumor of cartilaginous origin and represents less than 0.5% of all bone tumors.¹ It usually presents in patients during their second and third decade and has a predilection for the metaphyseal region of the distal femur and proximal tibia. Chondromyxoid fibroma may occasionally have an intracortical or subperiosteal presentation. Intracortical involvement is the more common of these presentations with 14 cases reported.^2–12 By contrast, a subperiosteal location is extremely rare. Only four confirmed cases are reported (Table 1). We present 2 new cases of subperiosteal chondromyxoid fibroma.

TABLE 1.

Summary of Cases of Subperiosteal Chondromyxoid Fibroma

Authors	Year	Sex	Age	Location
Andrew et al.26	1982	M	33	Tibial tuberosity
Marin et al.10	1997	M	45	Tibial diaphysis
Marin et al.10	1997	M	25	Proximal humerus
Estrada-Villasenor et al.27	2005	M	4	Distal tibia
Current authors	2006	M	36	Distal tibia
Current authors	2006	M	45	Distal fibula

Case 1

A 36-year-old man presented with a two year history of intermittent right leg pain without any precipitating trauma or injury. The pain was along the medial border of the distal one third of the tibia and was mainly present on palpation. He denied pain on weightbearing or night pain. When present, the pain was an eight to nine out of 10. On physical examination, there was no visible or palpable soft tissue mass.

Plain radiographs of the tibia showed a 1.0cm subperiosteal blister on the surface of the medial cortex of the distal tibia (Figure 1). There was an overlying rim of periosteal new bone. There was no obvious soft tissue mass or associated swelling. An MRI revealed a 4 x 4.5 millimeter subperiosteal lesion on the medial surface of the tibia (Figure 2). It had a heterogeneous T1 signal, increased T2 signal, and it enhanced with intravenous contrast.

Figure 1.

Plain film of the leg of patient one shows a well-circumscribed 1.0cm lytic lesion on the surface of the medial cortex of the distal tibia (arrow). Cortical saucerization and a thin rim of periosteal new bone formation are present.

Figure 2.

Axial T2-weighted image of patient one showing a 4 x 4.5 millimeter well-circumscribed, homogenous, subperiosteal lesion on the medial surface of the tibia (arrow).

The patient underwent excisional biopsy of the lesion. Histologic examination of the biopsy tissue showed a chondromyxoid fibroma (Figure 3). Due to the possibility of local recurrence, the patient had a completion of the excision. There has been no recurrence after one year.

Figure 3.

Photomicrograph of subperiosteal chondromyxoid fibroma from patient one demonstrating spindle and stellate-shaped cells with bland cytologic features in a background of chondromyxoid tissue.

Case 2

A 45-year-old man presented with a history of chronic right ankle pain that he attributed to multiple ankle sprains and trauma from playing soccer. Plain films of the ankle (Figure 4) demonstrated chronic synovitis in the ankle region, as well as a small lytic lesion in the lateral distal fibula. MRI revealed an 8mm long lesion in the lateral cortex of the distal fibula. The lesion did not extend to the marrow cavity and the overlying periosteum was elevated. T1-weighted images revealed an intermediate signal, while T2-weighted images showed some areas of intermediate signal and some areas of increased intensity similar to bone marrow.

Figure 4.

Plain film of the ankle of patient 2 shows a small, well-circumscribed lytic lesion on the surface of the lateral distal fibula (arrow). Cortical saucerization is present.

The patient was thought to have an osteoid osteoma or fibrous cortical defect. During an excisional biopsy, a prominent, palpable distal fibular lesion was found. A 0.5cm soft area considered to be the nidus of an osteoid osteoma was excised. Wide curettage was then performed on the rest of the lesion. Histologic examination of the lesional tissue showed a chondromyxoid fibroma. There has been no recurrence after one year.

DISCUSSION

Jaffe and Lichtenstein gave the first account of chondromyxoid fibroma in 1948.13 Fifty years later Wu et al. reviewed 278 cases of chondromyxoid fibroma from the Mayo Clinic files and summarized the following general features of the lesion.¹⁴ It has a slight predilection for males over females (1.1:1) and its peak incidence is in the second and third decades of life. It usually is found in the long bones (46.9%), particularly the distal femur and proximal tibia, but a large number can also occur in flat bones (30.3%). Radiographically, it is usually an intraosseous lesion that is most often found in the metaphyseal region of long bones (88%). The lesion is typically purely lytic, with occasional instances of intralesional calcifications (35.3%). It is usually a well-circumscribed lesion, usually with a sclerotic rim. Cortical thinning and expansion are also commonly seen on plain films. Periosteal new bone formation, however, is rare. Histologically, the classic chondromyxoid fibroma has stellate or spindle-shaped cells arranged in lobules on a chondromyxoid background. Within the lobules, the neoplastic cells tend to be localized more toward the periphery. The lobules are separated by fibrous bands that contain blood vessels and sometimes multinucleated giant cells (56.8%).

A subperiosteal presentation is extremely rare for chondromyxoid fibromas. A small subperiosteal lesion on a long bone, therefore, is not likely to raise suspicion of a chondromyxoid fibroma. More likely, periosteal chondroma, periosteal myxoma, subperiosteal ganglion cyst, or subperiosteal osteoid osteomas are considered.

Periosteal chondroma is a benign cartilage tumor that develops under the periosteum of long or short tubular bones.¹⁵ The most frequently affected site is the proximal humerus.¹⁶ This rare tumor, which accounts for less than 1% of all chondromas, typically affects males in the second and third decades of life.¹⁷ Since they are frequently found at tendon insertion sites, a palpable mass and pain at the site during activity are often the presenting symptoms.¹⁷ Radiographically, they present as a well-circumscribed lesion on the bone surface with punctuate calcifications; cortical saucerization is also often present.¹⁸ Histologically, they exhibit lobules of hyaline cartilage.¹⁵ A feature which helps distinguishing it from a periosteal chondromyxoid fibroma which lacks mature hyaline cartilage.

Periosteal myxoma is another lesion that can present on the bone surface. Myxomas are rare connective tissue tumors. When in the long bones, they tend to affect children more frequently, and often present with rapid onset pain and swelling.^19,20 Radiographically, they can present with a profuse periosteal reaction, which increases the thickness of the underlying cortex.¹⁹ Histologically, they are characterized by stellate cells within a loose mucoid stroma.¹⁹ Chondroid tissue is noticeably absent, which a key feature that distinguishes it from a periosteal chondromyxoid fibroma.

Subperiosteal ganglion cysts are coalescing cavities of jelly-like material that are thought to be the result of mucoid degeneration and cyst formation of the periosteum. Radiographically, they are surface lesions that produce external cortical scalloping and a periosteal new bone reaction.²¹ They usually present as palpable, but painless, masses.²² Cross-sectional imaging provides the definitive diagnosis by revealing the purely cystic nature of the lesion.

Osteoid osteoma is a benign osteoid forming tumor that usually arises in the cortex or adjacent medullary cavity of the femur or tibia. A subperiosteal origin is less likely, but not uncommon.²³ Like the conventional version, subperiosteal osteoid osteomas also present as a localized bone pain in a young person.²⁴ This pain is often dramatically relieved by aspirin. Radiographically, it is a lytic lesion on the surface of the bone that causes cortical erosion and an adjacent periosteal reaction.²⁴ CT is diagnostic as it reveals the nidus at the center of the lesion.²⁵ Histologically, there is a varied pattern of fibrovascular stroma, reactive bone, and varying amounts of mineralization of the nidus, which tends to be smaller than those of conventional osteoid osteomas.²⁴

When confronted with a small subperiosteal lytic lesion on a long bone, orthopaedic surgeons, pathologists, and radiologists are more likely to consider periosteal chondroma, periosteal myxoma, subperiosteal ganglion cyst, or subperiosteal osteoid osteoma. However, our two cases and the four previously reported cases illustrate that chondromyxoid fibroma should also be included in the differential diagnoses of a small, scalloped surface lesion.