Chest wall lump: lipoma or intramuscular myxoma?

Intramuscular myxomas (IM) of the chest wall are extremely rare. We present the case of a 58-year-old African-American female who was initially diagnosed with having a chest wall lipoma. After re-evaluation, the lesion was consistent with an intercostal myxoma versus myxoid sarcoma. Preoperative imaging could not exclude malignancy. Given the diagnostic uncertainty, she underwent primary wide local resection and placement of polypropylene mesh for chest wall reconstruction. Histopathological examination revealed an intramuscular myxoma without sarcomatous changes arising from the 8th intercostal muscle bundle.