Case 207 - Discussion

Uploaded: 2008-05-03, Updated: 2008-06-22

Diagnosis: Cytomegalovirus Pneumonia and Pneumocystis Pneumonia

Pneumocystis Pneumonia

• Intra-alveolar frothy infiltrates with a bubbly, vacuolated appearance;

• Alveolar septa with pneumocyte hyperplasia and mild chronic inflammation;

• Pneumocystis jiroveci:

  • Formerly carinii, belongs to fungi rather than protozoa;

  • 5-8 um, central dark dot, grooves and folds, partially collapsed cyst with helmet and crescent shapes, no budding;

  • GMS positive.

• May show a wild range of histologic features: frothy exudates in the interstitium or alveolar spaces, necrotizing granuloma, diffuse alveolar damage, or minimal histologic damage.

Pulmonary Alveolar Proteinosis (PAP)

• Intra-alveolar accumulation of lipid-rich, surfactant like material, due to increased surfactant production or impaired clearance;

• Intra-alveolar accumulations of eosinophilic material, coarsely granular, large granules, sharply round empty spaces, cholesterol clefts;

• No marked interstitial inflammatory infiltrates;

• PAS positive, surfactant apoprotein posiitive.

• EM: concentrically laminated myelin and lamellar bodies;

• May be associated with nocardia infection.

Cytomegalovirus Pneumonia

• Miliary pattern: multicentric lesions with alveolar exudates composed of fibrin and mixed inflammatory cells; central necrosis; classic CMV inclusions;

• Diffuse interstitial pattern: mildly to fully developed damage; type II pneumocyte hyperplasia, CMV inclusions;

• CMV antibody positive;

• Differential diagnosis of inclusions:

  • CMV inclusion: enlarged nuclei, large eosinophilic to basophilic nuclear inclusions surrounded by a halo; frequent intracytoplasmic inclusions;

  • HSV inclusion: multinucleation, margination, molding; intranuclear eosinophilic inclusion, not intracytoplasmic;

  • RSV: multinucleation, eosinophilic intracytoplasmic inclusions with perinuclear arrangement, not intranuclear;

  • Adenovirus: smudge cells with basophilic inclusion that obscures the nuclear membrane; or eosinophilic inclusions surrounded by a clear halo that resemble CMV or HSV;

  • Measles: extremely large multinucleated giant cells with both nuclear and cytoplasmic inclusions, the intranuclear inclusions are eosinophic with a clear halo, the cytoplasmic inclusions are eosinophilic, granular in variable sizes.

Adenovirus Pneumonia

• Necrotizing bronchitis and bronchiolitis;

• Interstitial pneumonia with necrosis, hemorrhage, and diffuse alveolar damage;

• Smudge cells: basophilic inclusion that obscures the nuclear membrane, may have halo.

References

• PIP, 2008-A;

• Non-Neoplastic Disorders of the Lower Respiratory Tract, series 4.