46. CMV lung

Staining: HE

Overview of the slide

Organ: Lung

Description:

Only a small region in the upper left corner shows healthy lung parenchyme. The rest of the slide shows inflammation of the lung interstitium, the alveolar septa. The interstitium is so thickened that the majority of the slide is interstitium, not alveolar spaces. The alveolar spaces are empty.

A special cell morphology called “Owl’s eye” can be seen. These cells are enlarged and have inclusion bodies inside the nucleus.

Diagnosis: Cytomegalovirus pneumonitis

Compare the alveoli of the unaffected part of the lung and the affected part. The alveoli in the unaffected lung have their characteristic wiggly shapes. The alveoli in the inflamed interstitium are round, because the interstitium has been enlarged, which has stretched the alveolar septa.

Risk factors: Immunosuppression

Theory:

Cytomegalovirus doesn’t cause pneumonia, it causes pneumonitis, because it’s the interstitium that’s inflamed and not the alveolar space. Cells infected by the virus become very large, and accumulate inclusion bodies, which are aggregates of protein that are visible macroscopically.

Yes, these are alveoli

Owl’s eye morphology. Note the large size and the white “halo” around the nucleolus.

Another Owl's eye. Note the inclusion bodies inside the cytoplasm