Speaking of granulomatous lung disease (previous post), Hartel et al. have written a clinicopathologic review of the largest published series (20) of cases of pulmonary granulomatous inflammation associated with Pneumocystits jiroveci (formerly known as Prince).
I recall first seeing a case of Pneumocystis pulmonary granulomatous inflammation in an Illinois Registry of Anatomic Pathology case probably about 17-18 years ago--apparently, it made quite an impression! Of course, I've only seen one similar case since them "in real life."
Several important findings from the paper:
- The granulomas were well-formed in 80% of cases, necrotizing in 80% of cases, and multiple in 90% of cases.
- Radiographic appearance is atypical for Pneumocystis pneumonia: Nodular infiltrates were present in 50% (8/16) of cases with studies and a solitary nodule was present in 19% of cases (3/16).
- Open biopsy was required to make the diagnosis in 65% of cases and the diagnosis was made at autopsy in 25%. Bronchoalveolar lavage--the main diagnostic tool in conventional Pneumocystis pneumonia--is of low yield in the diagnosis of granulomatous Pneumocystis pneumonia--as are bronchial washings, FNA, and transbronchial biopsy. The fact that these tests are usually negative in this setting may explain why the diagnosis was made post-mortem a quarter of the time.
- The authors discuss the role of host factors as most likely contributing to the atypical pathological manifestations of Pneumocystis since studies have repeatedly concluded that identical organisms are present in the various histologic reactions identified.
- Good discussion of distinguishing between P. jiroveci and H. capsulatum on GMS stain: the lack of budding forms, shape and size (Pneumocystis--spherical, Histoplasma--ovoid)of yeast, and size of capsular dots (larger in Pneumocystis versus Histoplasma).