Which tumor is associated with a "soap bubble" appearance on imaging?

• A. Giant cell tumor
• B. Osteosarcoma
• C. Chondromyxoid fibroma
• D. Both A and C

Answer: (D)

The "soap bubble" appearance on imaging is particularly characteristic of giant cell tumors and chondromyxoid fibromas. These tumors are often noted for their distinct radiological features, which can include lytic lesions with a multi-locular appearance, resembling soap bubbles.

Giant cell tumors typically present around the knee and are known to cause extensive bone destruction, leading to this classic appearance. Similarly, chondromyxoid fibromas, which are rarer and usually found in the metaphysis of long bones, can also show a similar radiographic feature with lytic lesions that separate into distinct compartments.

Osteosarcoma, on the other hand, is usually associated with a more aggressive pattern on imaging that includes a sunburst appearance or Codman's triangle, rather than the soap bubble configuration. Given this context, recognizing that both giant cell tumors and chondromyxoid fibromas can lead to the "soap bubble" appearance confirms that the answer is inclusive of both tumor types in the options presented.