Pathology and Pathogenesis of Pulmonary Aspergillosis
In its early stage, the lesion of pulmonary aspergillosis is diffuse infiltrative and exudative change, and in its advanced stage, the lesion is necrosis, suppuration, or granuloma. In the lesion, a large quantity of hyphae can be found. Penetration of the hyphae into vascular vessel may cause vasculitis, perivasculitis, and thrombus (fungal embolus) formation. Thrombus (fungal embolus) formation further induces tissue ischemia and necrosis. Pathologically, based on invasion of aspergillus hyphae into lung tissue (invasion of basilar membrane of bronchial epithelium in the airway), pulmonary aspergillosis is classified into invasive and noninvasive types. Invasive pulmonary aspergillosis is commonly acute and can be further grouped into vascular invasive and airway-invasive subtypes. Noninvasive pulmonary aspergillosis is commonly chronic, with the hyphae confined within original lung cavities that do not invade other lung tissues. There is intermedius type in invasive and noninvasive pulmonary aspergillosis, which is known as subacute invasive pulmonary aspergillosis or chronic necrotizing pulmonary aspergillosis.