Atypical histologic presentation of Pneumocystis pneumonia as granulomatous lung nodules

Abstract Pneumocystis jiroveci pneumonia (PJP) is classically described as presenting histopathologically as frothy intra-alveolar exudates. Less commonly, it can present with focal granulomatous lesions in patients with or without underlying acquired immune deficiency syndrome (AIDS). Here we present a series of cases of granulomatous PJP in patients without AIDS and describe the key features for diagnosis by histopathology. Histopathology and microbiologic cultures were performed by standard methods. Molecular confirmation of identification was performed by polymerase chain reaction of the fungal ribosomal RNA gene or cdc2 gene. Three patients are presented with various causes of immunosuppression who developed granulomatous PJP. The pathology and staining results are reviewed, along with the corollary information required for final diagnosis. Granulomatous inflammation is an under-recognized, but not entirely rare, presentation of PJP. Pathologists must be aware of this entity and must be prepared to make the diagnosis in cases where clinical suspicion is low and to differentiate it from other common infectious causes of lung granulomata. Molecular confirmation may be required when histomorphology is not definitive.