Orthopedic Teaching Cases 2023, Jan, 18 | 12:00 am

Orthopedic Oncology cases schwannoma

A 38-year-old female is referred to your office by her primary physician for a mass on her neck. It is painless and nontender to palpation. It is very firm on examination, and she reports that it has been slowly growing over 2 years. She brings an MRI ordered by her primary physician for your review (Fig. 8–25A and B).

 

 

 

 

Figure 8–25 A–B

 

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 preferences as to which method they utilize under which circumstances.

 

Objectives: Did you learn...?

 

 

Clinical and imaging features of desmoid tumor? Treatment options for desmoid fibromatosis?

 

Differences between pre- and postoperative radiation treatment?

 

CASE                               21                               

A 40-year-old male presents to your office with a chief complaint of pain and tingling down his left arm. He complains of some numbness at his fingertips. He notes that about 6 months ago, he noticed a growing lump in his upper arm. It has

been growing slowly over time, and his symptoms have gotten worse. The area is relatively tender to palpation, and there is a positive Tinel sign with deep palpation of the mass, replicating his symptoms. MRI is shown in Figure 8–26A and B.

 

 

 

 

Figure 8–26 A–B

 

What is the likely diagnosis?

  1. Angiosarcoma

  2. Neurofibroma

  3. Hemangioma

  4. Schwannoma

 

Discussion

The correct answer is (D). The history suggests a nerve tumor based on the neurologic symptoms and the Tinel sign. The MRI shows characteristic findings of Schwannoma as discussed below.

Which of the following are not characteristic MRI findings?

  1. Continuity with the affected nerve

  2. “Split fat” sign with fat signal seen on either end of an oval mass

  3. Central “target” seen on T1 images

  4. Infiltrative pattern eroding into neighboring bone

 

Discussion

The correct answer is (D). Schwannoma is a benign soft-tissue tumor of Schwann cells. These tumors grow eccentrically from the nerve sheath and do not involve the nerve fibers themselves, therefore they can be surgically removed from the neighboring nerve, usually without causing any permanent nerve damage. Imaging studies reveal an oval mass which can often be seen to be continuous with a nerve fiber. A “split fat” sign is usually seen and can help make the diagnosis. These tumors demonstrate low signal intensity on T1 and high signal intensity on T2, with diffuse gadolinium enhancement. A central target may be seen on T1-weighted images, which is well demonstrated in this study. The tumor can produce peripheral nerve symptoms, and are generally firm and quite painful. Tapping the tumor with a finger can reproduce the nerve symptoms, which is called a Tinel sign. These tumors are benign and do not grow in an infiltrative pattern into neighboring bone.

Histologic examination performed on an incisional biopsy sample from the lesion reveals palisading and distinct Antoni A and Antoni B areas. What staining antibody could be used to support the diagnosis?

  1. CD-28

  2. S-100

  3. CD-99

  4. Schwann cells disintegrate with immunohistochemical staining, therefore no test is indicated

Discussion

The correct answer is (B). Schwannomas and other nerve tumors strongly stain positive for the S100 antibody. Although S-100 is not diagnostic of schwannoma, in the setting of appropriate imaging and histology, it is supportive of the diagnosis. CD-28 is used to aid in the diagnosis of multiple myeloma, and CD-99 is associated with Ewing sarcoma.

 

Objectives: Did you learn...?

 

 

Clinical and imaging features of schwannoma? Histological features of schwannoma?