In the neutropenic patient, hemorrhagic, coagulative necrosis is the rule. When PMNs return, they may surround and digest the peripheral necrotic tissue to produce a lung ball . In the non-neutropenic host, a neutrophilic pneumonia without a fibrous wall or with variable degrees of walling off by granulation tissue occurs. Cavitation may occur secondarily. The organisms ignore lobar and pleural boundaries in local spread, and they invade vessels and spread to other organs.
Vascular invasion is associated with thrombosis and angiitis.
Two subpleural nodules that developed during a period of neutropenia are shown here. A plain film showed fewer opacities. All cultures and bronchial lavages were negative, and the nodule on the right was biopsied after the PMNs had returned. A GMS stain showed a few degenerating organisms that resembled aspergillus. The inset shows the PMNs at a higher magnification.