About 90 days post-bone marrow transplant, a 55-year-old white woman began to complain of dry cough, shortness of breath, and chest pain. She was started on antibiotics and blood culture obtained at the time was negative and there was not improvement. A computed tomography (CT) scan of the lungs showed a halo of low attenuation around a nodular lesion. Analysis of lung biopsy was similar to methenamine silver-stained section below. The most likely diagnosis for this patient is