February 2016 Case of the Month

53 year-old man presents with fatigue,cough, and cavitary lung lesions, status post bronchoscopy with biopsy and lavage.  What is your diagnosis?

4x
4x

Low power view of a transbronchial biopsy specimen showing caseating necrosis.

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10x

Necrosis composed of degenerating cellular debris. Obvious granulomas are not readily apparent.

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BAL AFB 100x
BAL AFB 100x

The BAL specimen showed frequent AFB positive rods within the histiocytes.

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4x

Low power view of a transbronchial biopsy specimen showing caseating necrosis.

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February 2016 Case of the Month

   Answer: Pulmonary Tuberculosis

The presence of caseating necrosis in a lung biopsy warrants the performance of both acid-fast (AFB) and GMS special stains to rule in/out microorganisms.  In this case, numerous acid-fast rods were identified, mostly in the bronchial lavage specimen.  Given the initial radiologic impression, the patient was immediately placed into isolation until a definitive diagnosis was made.  The lavage tissue block was also sent for M. tuberculosis complex PCR, which was positive.  The patient was started on combination antibiotic therapy, including isoniazid and rifampicin.  Tuberculosis, historically called consumption, has been a serious infectious disease to humans since time immemorial and caused nearly a quarter of all deaths prior to the advent of antibiotic therapy.  The bacteria was originally discovered by Dr. Robert Koch and the first antibiotic (streptomycin) was derived from the soil bacterium Streptomyces griseus.  Most patients infected with susceptible strains will recover if maintained on combination antimicrobial therapy for the prescribed 6 months.