Objective: To determine the frequency of positive microbiologic cultures in patients with epithelioid granulomas and negative histochemical stains for microorganisms in transbronchial biopsy specimens. Secondary objectives were to compare the histologic features of sarcoidosis with those of infectious granulomas and to assess the reliability of histology in establishing the diagnosis of sarcoidosis.
Design: Retrospective study. Specific histologic features of transbronchial biopsy specimens were correlated with clinical and microbiologic data, final diagnosis, and an estimate of the probability, on admission, that the patient had sarcoidosis.
Setting: A large, urban, tertiary-care, university-affiliated hospital.
Patients: Ninety-two adult patients in whom epithelioid granulomas, negative for microorganisms on Ziehl-Neelsen and Gomori methemaine silver stain, were found in transbronchial biopsy specimens. Patients were identified through a search of surgical pathology files from 1975 to 1987.
Results: Ten patients (10.9%) had mycobacterial or fungal granulomas, while 82 had sarcoidosis. In all patients with a high clinical probability of sarcoidosis, the diagnosis was confirmed. Transbronchial biopsy specimens from patients with infectious granulomas had fewer granulomas (2.0 +/- 1.7 (SD) versus 7.1 +/- 6.6; P<.01), which involved a smaller proportion of lung tissue per case (9.5 +/- 10.0% versus 26.6 +/- 24.0%; P<.01). Sarcoid granulomas often exhibited Schaumann bodies (69.5% versus 10%; P<.01). Necrosis tended to predominate in infectious granulomas (19.5 versus 40%; not significant).
Conclusions: Numerous granulomas, Schaumann bodies, and a high clinical probability of sarcoidosis are significantly associated with that diagnosis. Necrosis does not exclude sarcoidosis. Clinicopathologic assessment of transbronchial biopsy specimens is useful in predicting the final diagnosis of sarcoidosis but does not obviate the need for microbiologic cultures, which were positive in 10.9% of patients in this study.