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A 48-year-old gentleman with a history of hepatocellular carcinoma status post orthotopic heart transplant, was noted on further chest CT-imaging to have 2 new lesions within his right upper lobe. Clinically, these lesions were suspected to be metastases. He underwent right upper lobe wedge resection. Pathologic examination did not reveal any grossly apparent lesions or masses. The microscopic examination revealed significant pathologic features as below (Figures 1-4 H&E, Figure 5 GMS, Figure 6 Mucicarmine),

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1. What is the most likely cause for this granulomatous inflammation?

  • A. Blastomyces sp. Infection
  • B. Cryptococcus sp. Infection
  • C. Histoplasma sp. Infection
  • D. Candida sp. Infection

2. What is the most important feature/s pointing towards the likely organism?

  • A. Larger yeasts (8-15 µm), double contoured refractile cell wall, broad based budding
  • B. Presence of a capsule, narrow-based budding, variable sizes of yeasts
  • C. Intact spherules, old spherule walls, endospores
  • D. Smaller oval yeasts (2-7 µm), narrow-based budding, uniform size of yeasts

3. What do you do if the histochemical stains are negative in necrotizing granulomas that looks infectious?

  • A. Carefully examine the granulomas to see features of other than infections (vasculitis for Granulomatosis with Polyangiitis).
  • B. Consider doing additional special stains for micro-organisms in more than one block to include the areas of necrosis.
  • C. Clinical suspicion of infection is high, but stains are negative, then consider doing additional molecular tests (PCR for M. TB).
  • D. Clinical correlation with cultures and serologic testing will be beneficial.