Aspergilloma (fungus ball) is what Aspergillus fumigatus causes in the immunocompetent individual with abnormal lungs, whether it is due to a cavity of previous TB, sarcoidosis, bronchiectasis, etc. 

Monad sign is what describes the air that surrounds the soft tissue mass. Remember that the fungus ball is mobile, so that on an erect chest x-ray, the mass will be inferior and the gas rim is superior.