Slide 203.Tuberculosis, Lung

A. Brief Descriptions

  1. Caused by Mycobacterium tuberculosis.

B. Gross Findings

  1. Primary TB – Ghon complex.

  2. Secondary TB – in the apex as a small focus of consolidation.

C. Micro Findings

  1. Granulomas (tubercles):

    1. Central caseation necrosis.

    2. Epithelioid histiocytes.

    3. Multinucleated Langhans’ giant cells.

    4. Fibroblasts and lymphocytes.

E. Reference

  1. Robbins Pathologic Basis of Disease, 6th ed.  P.379-352.




Fig. 203-1 (LP)Multiple confluent or separated nodules are seen in lung parenchyma. Note thickened and congested interstitium. The alveoli show emphysematous change.



Fig. 203-2 (LP)Caseating granuloma (tubercle). The center of the tubercle contains caseous necrotic debris (amorphous eosinophilic substance) and is surrounded by epithelioid histiocytes and lymphocytes.




Fig. 203-3 (LP)The center of the tubercle is composed of caseating necrotic debris. Note the elongated epithelioid histiocytes around the caseating center.



Fig. 203-4 (LP)A caseous granuloma with caseating necrotic center, epithelioid histiocytes and a typical Langhans’ giant cell (middle left). Note the nuclei of the Langhans’ type giant cell lined in horseshoe arrangement.




Fig. 203-5 (HP, acid fast stain)The acid fast stain highlights bacilli of Mycobacterium species (pink color) (Most commonly M. tuberculosis).