Foot and Ankle cases 31

A 54-year-old male presents with right forefoot pain, swelling, and a sense of pressure. He reports that he was previously evaluated by a podiatrist who aspirated fluid from a lump in his foot, but that the lump subsequently recurred. The patient arrives with a foot x-ray (Fig. 5–61) and MRI (Figs. 5–62 and 5–63).

 

 

 

Figure 5–61 AP radiograph of the foot.

 

 

Figure 5–62 MRI coronal foot T1 image.

 

 

 

 

Figure 5–63 MRI coronal foot T2 fat-suppressed image.

 

What is the most likely diagnosis?

1. Angiosarcoma

2. Ganglion cyst

3. Clear cell sarcoma

4. Lipoma

 

Discussion

The correct answer is (B). Unlike other areas of the body that may have higher concentrations of somatic tissue, the foot has a high concentration of tendons, fascia, and synovium. Ganglion cysts consist of mucinous fluid intimately connected with a joint or, more frequently in the foot, a tendon sheath. The foot is

the third most common place for ganglion cysts after the hand and wrist. On MRI ganglions can be round, lobulated, or septated, but generally have a sharp outline with clear T2 signal.

Had the above lesion been similar in shape on MRI, but bright on T1 and dark on T2, what would be the most likely diagnosis?

1. Angiosarcoma

2. Ganglion cyst

3. Clear cell sarcoma

4. Lipoma

 

Discussion

The correct answer is (D). Lipomas generally show a signal intensity similar to normal fat, which is bright on T1 and dark on T2. Areas of inflammation or fibrosis, however, can make some lipomas more difficult to distinguish from liposarcomas.

Giant cell tumor (GCT) of tendon sheath is an extra-articular tumor that can be found in the foot. What is its intra-articular equivalent?

1. Pigmented villonodular synovitis

2. Synovial sarcoma

3. Clear cell sarcoma

4. Ganglion cyst

 

Discussion

The correct answer is (A). GCTs of tendon sheath are of synovial origin and may arise from tendon sheaths as well as ligaments bursa, and joint capsules. This tumor is commonly found in the hand, where it has a low recurrence rate after resection. In the lower extremity it is the most commonly found tumor in the digits, but can also occur elsewhere in the foot. A nonfocal, diffuse and infiltrative variety (florid proliferative synovitis) is thought to be an extra-articular version of pigmented villonodular synovitis. Characteristic appearance on MRI includes inhomogenous T1 and T2 signals with solid areas as well as areas of tumor necrosis. Its pathologic appearance is highly vascular with interspersed giant cells, macrophages, fibroblasts, and deposits of hemosiderin.

 

Objectives: Did you learn...?

 

 

Identify MRI appearance of common benign lesions in the foot? Describe the pathologic origin of some foot and ankle tumors?