Orthopedic Oncology cases tumor mimickers

An athletic 24-year-old male is referred from his doctor’s office for an abnormal finding on radiographs of his shoulder. His only recent history is that 6 weeks ago he sustained a direct blow to the shoulder by a pitch during a baseball game. The patient has noticed a firm mass in this area, which has been growing in size, and x-rays taken yesterday reveal a mass in the soft tissue of the shoulder. X-rays are shown in Figure 8–28A and B.

 

 

 

Figure 8–28 A–B

 

What is the most likely diagnosis, based on history, physical examination, and radiographs?

1. Intramuscular hemangioma

2. Ewing sarcoma

3. Parosteal osteosarcoma

4. Myositis ossificans

 

Discussion

The correct answer is (D). Myositis ossificans is a reactive process characterized by a well-circumscribed proliferation of fibroblasts, cartilage, and bone within a muscle, thought to be due to maturation and mineralization of a hematoma or bleeding into the muscle. It is a posttraumatic condition, and presents with pain, tenderness, swelling, and a growing firm mass within the soft tissues. Radiographic examination reveals an irregular, fluffy density in the soft tissues, which develops over time into increased peripheral mineralization and a radiolucent center. This peripheral pattern of mineralization has been called to a “rose” pattern.

What is the natural history of this lesion?

1. It is a self-limited process

2. It is benign but locally aggressive and can erode nearby cortex or destroy nearby joints

3. It has high metastatic potential

4. It does have a low risk of benign metastasis to lungs

 

Discussion

The correct answer is (A). Myositis ossificans is a self-limited, benign process, so observation and physical therapy to maintain motion are indicated. This is a diagnosis that can be made on history, physical examination, and radiology studies most of the time, without need for biopsy.

Management at this point should consist of:

1. Biopsy followed by wide excision

2. Radiation followed by wide excision

3. Physical therapy and observation, with repeat radiographs

4. Chest CT and wide excision if CT is negative

 

Discussion

The correct answer is (C). Physical therapy and observation are the only necessary treatments indicated at this point. Physical therapy will maintain range of motion of

the shoulder, as this lesion can be painful, and patients will self-limit their physical activity. Often, the size of the mass decreases after 1 year. Follow-up radiographs must be conducted to confirm maturation and stability of the lesion. Excision is only indicated once the lesion is mature (6–12 months) and only if the patient is symptomatic. Local recurrence rates increase if excision is performed in the initial stages.

Follow-up x-rays are obtained in 3-month intervals for the next 6 months. What would you expect to see?

1. Progressive mineralization of the periphery with a radiolucent center, followed by eventual mineralization of the center then resolution

2. Progressive growth and eventual destruction of the neighboring femoral cortex

3. Persistence of the mineralized mass without change over time

4. Pathologic fracture of the humerus

 

Discussion

The correct answer is (A). The radiographic characteristics of myositis ossificans evolve in a predictable pattern. The lesion initially appears as an irregular, fluffy density in the soft tissues. Over time, it organizes into a zonal pattern, displaying rimmed mineralization of the periphery with a radiolucent center. Eventually, the center will mineralize, and eventually the lesion will regress. Monitoring this predictable pattern gives reassurance that the lesion is indeed myositis ossificans.

 

Objectives: Did you learn...?

 

 

To identify important tumor mimickers: infection, myositis ossificant? Imaging features of myositis ossificans?

 

Treatment of myositis ossificans?