Fibrosing, Necrotizing Pneumocystis Pneumonia

Acute pneumocystis pneumonia may lead to focal organization and fibrosis. Several patterns may be seen within these fibrotic nodules. The three examples shown here are from the same patient.

A 64-year-old man with AIDS and pneumocystis pneumonia was treated until his death 3 months later with Bactrim and azidothymidine. CD 4 count was 50 cells/µl. At autopsy, scattered miliary nodules and larger nodules up to 1 cm in diameter, some with cavities, were found.


Figure 1. Focal Histiocytes and Necrosis

All nodules were composed of fibrous tissue with moderate numbers of lymphoid cells. Here, within one such nodule is a granuloma-like focus of vacuolated macrophages surrounding a central zone of necrosis with a focal calcification. Multinucleated giant cells are absent. This lesion probably represents a local response to dead organisms.

Outline the granuloma-like focus.

Although this pattern suggests granuloma formation, it does not qualify as a typical granuloma because of the absence of epithelioid (with solid pink, rather than vacuolated, cytoplasm) histiocytes and multinucleated giant cells.

Figure 2. Nodule with Necrosis

In another nodule, calcifications dot the inflamed fibrous wall that surrounds a large area of necrosis. Within the necrotic area some architectural elements remain, suggesting ischemic coagulative necrosis.



In the necrotic portion, note the dense pink clumps. These represent condensation of pink alveolar foam of pneumocystis. Some of the clumps have calcified.

Find the dense pink, calcifying clumps in the necrotic zone.

Figure 3. Cavitation

Cavities have thicker walls (>1mm) than cysts. Cavities may arise in pre-existing fibrotic nodules or represent fibrosis around a cyst that arose earlier.



Here, a cavity is present. It has a cellular wall of histiocytes and chronic inflammatory cells with focal calcifications, and is embedded in diffuse fibrous tissue. Note an airway and vessel at the upper left.

Outline the cavity with calcifications in the wall.


Return to Histology

TOP----Rad/Path Home Page































Granuloma-like lesion






























Clumped and calcifying foamy exudate of pneumocystis




























Cavity with calcifications in wall