Case 77. 
Non-tuberculous mycobacterial infection of lung (22 y-o M)
Apical lung lesions surgically resected after prolonged chemotherapy
Key words : 
Non-tuberculous mycobacterium, Mycobacterium avium-intercellulare, caseous necrosis    
opportunistic infection
The caseous lesions are grossly indistinguishable from tuberculosis.   Histologically, caseous necrosis and epithelioid granulomatous reaction with Langhans-type giant cells are observed, being totally indistinguishable from tuberculosis (HE).
A few acid-fast bacilli are identified in the cytoplasm of macrophages (Ziehl-Neelsen). M. avium-intracellulare was cultured from the lesion.   Reference case 77A
Autopsied lung of a 79 y-o male who died of massive hemoptysis (HE). Caseous necrosis is formed adjacent to the bronchus. Epithelioid cell reaction is incomplete in this case. M. avium-intracellulare was cultured.
Reference case 77B
Striated histiocytes in Mycobacterium avium-intracellulare infection in a 45 y-o AIDS guy (HE). Histiocytoma-like proliferation of histiocytes with striated eosinophilic cytoplasm is seen in the enlarged mediastinal lymph node.
  Reference case 77B
Acid-fast bacilli filling the cytoplasm of the striated histiocytes (Ziehl-Neelsen). The striated appearance of striated histiocytes is due to impaction of Mycobacterium in the cytoplasm.
Reference case 77B
BCG antigens identified in the cytoplasm of the striated histocytes (immunostaining). BCG antigens recognized by a polyclonal antibody from DakoCytomation are seen on the surface of Mycobacteria and some fungi, but not on human cells.
  Reference case 77B
Ultrastructural localization of BCG antigens on bacilliform microbes in paraffin section (pre-embedding immunoelectron microscopy). Structures of microbes are relatively resistant to paraffin embedding. Pre-embedding immunoelectron microscopy using paraffin sections is useful to show the specificity of immunostaining.