CTICasesNecrotizing Granulomatous Pneumocystis jirovecii Pneumonia (PJP)
Imaging findings
CT images demonstrate bilateral, scattered, well-circumscribed lung nodules that are very upper lobe predominant. Biopsy from a nodule reveals necrotizing granulomas. High-magnification GMS stain of the granulomas shows tiny, oval, helmet-like cyst structures with central dots characteristic of Pneumocystis jirovecii nested within the necrotic centers of the granulomas.
Key takeaways
Although Pneumocystis jirovecii pneumonia classically presents as diffuse ground-glass opacities representing alveolar exudate, it can atypically manifest as solitary or multiple necrotizing granulomas, particularly in patients with altered or suppressed immunity (such as post-stem cell transplant). In such contexts, PJP should be considered in the differential of upper-lobe predominant granulomatous disease, and high-power pathology/GMS stains are essential for identifying the cysts buried within the necrotic centers.
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