Lung - nontumor
Infections
Tuberculosis (TB)

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 28 February 2017, last major update September 2011

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed search: tuberculosis [title] pulmonary infection

Related topics: Secondary (reactivation) pulmonary TB, Progressive pulmonary TB, Tuberculomas
Cite this page: Tuberculosis (TB). PathologyOutlines.com website. http://pathologyoutlines.com/topic/lungnontumorTB.html. Accessed June 24th, 2017.
Definition / general
  • Due to Mycobacteria tuberculosis
  • In developing world, M. bovis causes oropharyngeal and intestinal TB
  • Very prevalent, approximately 1.7 billion people are infected with 9 million new cases a year with an estimated 1.6 million deaths
  • In the United States, there are 11,000 new cases of active TB each year
  • Transmission is from person to person via airborn droplets, infections may be dormant for years
  • Infection does not mean disease; most infected individuals are asyptomatic; the genetic makeup of the host affects disease severity
  • TB is often a disease of poverty, overcrowding and associated with other chronic diseases
  • M. tuberculosis primarily infects macrophages
  • Lung involvement is the major cause of morbidity / mortality
  • Multidrug resistant TB and extensive drug resistant TB have recently emerged as clinical and public health challenges that have come about, at least in part from incomplete compliance with drug treatment regiments
  • Cases increasing due to AIDS and emergence of multidrug resistant strains; AIDS patients may lack granulomas
  • AIDS patients are more susceptible to TB and have more severe disease
  • There is also increased risk with alcoholism, immunosuppression (immunotherapy with TNF antagonists, lymphoma, especially Hodgkin lymphoma), chronic renal disease and chronic lung disease
  • Rarely involves skin, oropharynx and lymphoid tissue
  • Initial focus of infection is Ghon's complex, consisting of parenchymal subpleural lesion, near upper / lower lobe interlobar fissure (apex has high oxygen tension) with enlarged caseous lymph nodes
  • Lesions usually undergo fibrosis, calcification and cause no symptoms
  • Rarely (infants, children, immunocompromised), get progressive spread with cavitation, TB pneumonia and miliary TB
  • Screening: in much of the developed world Interferon-Gamma release assays have supplanted Mantoux Tuberculin skin testing
Treatment
  • Prolonged multiagent antibiotics
  • Lung resection indicated for: open cavity after 4 - 6 months of drug therapy, residual caseous disease, irreversible destructive lesion (bronchiectasis, bronchial stenosis), recurrent hemorrhage, unexpandable lobe with associated TB empyema, suspected tumor; surgical success rate (inactive disease) is 80% after 2 - 5 years
Gross description
  • Inflamed, fibrotic, nonfunctioning lung parenchyma
  • May have bronchial strictures, bronchiectasis, cavitation and thickened pleura
Gross images

Images hosted on other servers:

Multiple granulomas

Granulomas with caseous necrosis

Cavitation


Ghon's complex

Miliary TB

Microscopic (histologic) description
  • Caseating granulomas
  • Cavities show approximation of walls, granulation tissue, fibrosis and stellate scar
  • May have metaplastic bone formation