An adolescent female complains of pain and swelling in her ankle. This is giving her deep pain which she can no longer tolerate. She has constant pain which does not necessarily worsen with weight bearing. Imaging and workup is performed. NSAIDs have not helped her pain.

1. rays are shown in Figure 8–9. What kind of lesion is this?

   1. Osteochondroma

   2. Clear cell chondrosarcoma

   3. Chondromyxoid fibroma

   4. Chondroblastoma

Figure 8–9

Discussion

The correct answer is (C). Chondromyxoid fibroma is a rare, benign bone tumor that can be locally aggressive. It appears on radiographs as a lobulated lesion demonstrating expansive remodeling with areas of thinned cortex. Generally, a thin rim of cortex can be seen at the periphery of the lesion, but in aggressive cases this may not be so. Stippled calcification can be seen suggesting a cartilaginous matrix. It tends to be central when in short tubular or flat bones, and eccentric in the metaphyseal portion of long bones. Feet are a common location. Osteochondromas project outward from the bone. Chondroblastomas are typically epiphyseal lesions. Clear cell chondrosarcoma is a rare epiphyseal cartilaginous malignancy.

What is the most appropriate treatment?

1. Wide resection and reconstruction

2. Curettage and bone grafting

3. Observation

4. Bisphosphonates

Discussion

The correct answer is (B). Curettage and bone grafting is the standard treatment for chondromyxoid fibroma. This treatment is associated with a 25% recurrence risk, so patients must be monitored routinely postoperatively. Wide resection can be performed in aggressive cases in which curettage fails but is not the first line of treatment.

The appropriate operation is performed and the biopsy slide is shown in Figure 8–10A and B. Which of the following statements is true regarding this lesion?

1. Sheets of giant cells are seen

2. The lesion demonstrates a high mitotic index

3. Chondroid, myxoid, and fibrous regions can all be seen

4. Bland fibrous cells in a storiform pattern are characteristic

Figure 8–10 A–B

Discussion

The correct answer is (C). Microscopically, the lesions consist of prominent lobular areas of cartilage with surrounding fibrous and myxoid stroma. That is, chondroid, myxoid, and fibrous areas can all be seen on one low-power slide. The bland spindle cells arrange at the periphery of the cartilage matrix. Scattered giant cells may be seen, but sheets of giant cells are more indicative of a giant cell tumor. Atypia, mitotic figures or a high mitotic index, and necrosis are not seen here but are suggestive of a malignant tumor. Bland fibrous cells in a storiform pattern suggest a nonossifying fibroma.

Objectives: Did you learn...?

To recognize imaging and clinical features of chondromyxoid fibroma (CMF)? To recognize histologic features of CMF?

The appropriate treatment of CMF?

How to differentiate this lesion from other benign bone lesions?