Solving Complex Orthopedic Oncology Cases Schwannoma

What is the most likely diagnosis?

1. Desmoid tumor
2. Lipoma
3. Intramuscular hemangioma
4. Heterotopic ossification

Discussion

The correct answer is (A). Desmoid tumor is a benign but locally aggressive fibrous neoplasm that is most likely located on chest wall/back, shoulder girdle, abdominal wall, and thigh. They are two to three times more common in females, and median age is in the third decade of life. They display low signal intensity on T1, low to medium signal intensity on T2, and enhancement on postgadolinium studies. The slow, benign-growing nature of this tumor, imaging studies, physical examination, and demographic of the patient all support this being a desmoid tumor over the other options. However, desmoid tumor cannot be distinguished from soft-tissue sarcoma by imaging alone, and biopsy is needed prior to resection to obtain a firm diagnosis.

What is the best description of a desmoid tumor in terms of its growth potential?

1. Self-resolving with time
2. Malignant
3. Benign but locally aggressive
4. Locally aggressive until surgical resection, then very low recurrence rate

Discussion

The correct answer is (C). Desmoid tumors have a highly infiltrative growth pattern but do not metastasize and have no risk of malignant transformation. In many cases, they may be observed. When surgical resection is necessary, these tumors are treated with wide resection. In recurrent cases, or cases where a recurrence would be particularly difficult to address, external beam radiation may be considered.

The patient undergoes resection of the desmoid tumor from her neck. A year later, the lesion begins to recur in the same area but deeper. She undergoes a second resection, but due to the concern for possible involvement of the nearby cervical spine if the tumor were to recur again, the patient is also given external beam radiation. The approximate dose of radiation to the area is:

1. 600 rad
2. 6 Gy
3. 60 Gy
4. 600 Gy

Discussion

The correct answer is (C). The total amount of postoperative radiation for soft- tissue tumors is approximately 60 Gy. The preoperative radiation dose is approximately 50 Gy, because the postoperative bed is more hypoxic and requires a higher dose of radiation to achieve the same effect. The daily dose of radiation therapy is delivered in fractions of 200 cGy per day. For heterotopic ossification prophylaxis, the dose is about 600 cGy. (1 cGy = 1 rad.)

Which of the following is associated with preoperative as opposed to postoperative radiation for soft-tissue tumors?

1. Higher dose and larger field
2. Decreased wound healing rates
3. Improved local control of tumor
4. Decreased functional outcome long term

Discussion

The correct answer is (B). Preoperative and postoperative radiation therapy are associated with equivalent local control rates for soft-tissue sarcomas. However, the side effects associated with each method differ. Preoperative radiation therapy is associated with a smaller field and lower dose, but the wound infection risk is much higher at approximately 35%. There is decreased local fibrosis seen after preoperative radiation, resulting in an improved long-term functional outcome. Postoperative radiation is associated with a much lower wound risk at approximately 15% but is associated with a higher dose over a larger field because the postoperative bed is hypoxic, and the entire incision and region of dissection must be treated. Since local control rates are the same, both delivery methods are acceptable and individual centers have established their own p