Case 76. Tuberculosis of lung (65 y-o F)
         
   
Transbronchial lung biopsy from a lung nodule
   
         
   
Key words : 
Mycobacterium tuberculosis, pulmonary tuberculosis, encapsulated caseous focus, exudative tuberculosis    
     
 
     
Sarcoidosis was suspected by histologic features of non-caseous epithelioid granuloma with poor lymphocytic reaction (HE). However, the final diagnosis was tuberculosis (Acid-fast bacilli identified).   Brushing cytology contains clusters of epithelioid cells (Papanicolaou).
     
 
     
Reference case 76A
Caseous granuloma at the periphery of the lung (gross findings). Within the central caseation, pre-existing structures such as vessels and bronchioles can be traced, indicating coagulation necrosis.
  Reference case 76A
Caseous granuloma with epithelioid cells, Langhans-type giant cells and caseous necrosis (HE). In case of primary infection, the tuberculous granulomas are also formed in the regional hilar lymph nodes (so-called primary complex).
     
 
     
Reference case 76B
Old tuberculosis, representing an encapsulated caseous focus at the periphery of the lung (gross findings). In Japanese autopsy series, old tuberculosis is diagnosed in some 10% of cases, and infective lesions are seen in 1-2% of cases.
  Reference case 76B
Encapsulated caseous focus retaining the pre-existing alveolar structures (Elastica van Gieson). It is shown that caseous necrosis represents a special subtype of coagulation necrosis.
     
 
     
Reference case 76C
Encapsulated caseous focus, an incidental finding at autopsy (HE). This hyalinized tuberculous lesion can be regarded as non-infective (HE). Ziehl-Neelsen's stain failed to show acid-fast bacteria.
  Reference case 76C
Encapsulated caseous focus (immunostaining for BCG antigens). BCG antigens can be demonstrated in the old caseation (immunostaining). It is thought that mycobacterial antigens (components) remain locally for a long period of time.
     
 
     
Reference case 76D
Exudative tuberculosis in case of SLE after corticosteroid therapy (36 y-o F), accompanying high biohazard at autopsy (gross findings). Tuberculosis is highly activated by suppression of cell-mediated immunity, including steroid therapy and AIDS.
  Reference case 76D
Exudative tuberculosis in immunosuppression, histologically showing necrotic exudation without granulomatous reaction (HE). The lack of granulomatous reaction represents T-cell dysfunction.
     
 
     
Reference case 76D
Exudative tuberculosis in immunosuppression, containing an overwhelming number of acid-fast bacilli within the lesion (Ziehl-Neelsen). The lesion is highly biohazardous. The airborne transmission of M. tuberculosis should be avoided during autopsy by wearing the N95 particulate mask.
  Reference case 76E
Miliary tubersulosis in case of acute leukemia after chemotherapy (43 y-o M), indicating blood-borne systemic dissemination of mycobacteria (gross findings). Macroscopic recognition of tuberculosis of varied types is important to avoid unnecessary biohazard. The annual incidence of tuberculosis among Japanese pathologists and pathology technicians is as high as 600/100,000/year (roughly 30 times more than the general working age population).