The gray-white parenchymal focus is under the pleura in the lower part of the upper lobe. Hilar lymph nodes with caseation are seen on the left.
Primary pulmonary tuberculosis (Ghon complex)
A characteristic tubercle at low magnification (A) and in detail (B) illustrates central granular caseation (right) that is surrounded by epithelioid and multinucleated giant cells (left). This is the usual response seen in individuals who have developed cell-mediated immunity to the organism. C, Occasionally, even in immunocompetent individuals, tubercular granulomas may not show central caseation; hence, irrespective of the presence or absence of caseous necrosis, special stains for acid-fast organisms must be performed when granulomas are present in histologic sections.
The morphologic spectrum of tuberculosis
Multiple noncaseating epithelioid granuloma of TB
Note that the granulomas are enclosed within a fibroblastic rim with lymphocytes.Microscopically, caseous necrosis is characterized by acellular pink areas of necrosis, as seen here at the upper right, surrounded by a granulomatous inflammatory process.
Caseating epithelioid granuloma of TB
Mycobacterium tuberculosis: acid-fast stain
Note the red rods--hence the terminology acid fast bacilli (AFB)The upper parts of both lungs show multiple areas of softening and cavitation (arrows)
Secondary pulmonary tuberculosis
Lt. multitude of small (2 to 4 mm), yellow-white foci ; these scatter diffusely through the lungs. The miliary pattern gets its name from the resemblance of the granulomas to millet seeds. Rt. A zoom in appearance; the miliary pattern is seen throughout the lung.
Miliary pulmonary TB