Interesting. I too was recently diagnosed with a necrotizing granuloma that has caused a cavitation in my lung. It also came up MAC positive. My doctors (ID and pulmonologist) let it go untreated for 6 months but the followup CT scan showed that it doubled in growth. As a result i just started on the big 3 antibiotics to treat the MAC. I am also asymptomatic. I do not have bronchiectasis which seems to be a big risk factor for MAC but am an asthmatic and have been on inhaled steroids for 25 years. Thinking that is the cause for my infection. Good luck to you and keep us posted on your progress. Im very curious to hear if your granuloma goes away without treatment.