Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Radiology description | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Electron microscopy images | Videos | Differential diagnosis | Additional referencesCite this page: Yoshikawa A, Bychkov A. Emphysema. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungnontumoremphysema.html. Accessed January 24th, 2021.
Definition / general
- Pulmonary emphysema is defined as permanent abnormal enlargement of air spaces distal to the terminal bronchioles with destruction of the alveolar septa with little or no fibrosis
- In a broad sense, emphysema refers to the condition when air is abnormally introduced and trapped in the tissue; it can occur in any part of body such as subcutaneous soft tissue, mediastinum, epidural area and solid organs
Essential features
- Destruction of acinar structure and airspace enlargement, especially due to cigarette smoking
- Affects multiple pulmonary functions and causes chronic respiratory symptoms
Terminology
- Major types (Lancet 2004;364:709, Int J Chron Obstruct Pulmon Dis 2008;3:193):
- Centriacinar, centrilobular or proximal acinar emphysema (most associated with smoking and COPD)
- Panacinar or panlobular emphysema
- Paraseptal or distal acinar emphysema
- Minor types
- Combined pulmonary fibrosis and emphysema (CPFE)
- Interstitial emphysema
- Bullous emphysema
- Senile emphysema
- Irregular emphysema
- Congenital lobar emphysema
Epidemiology
- COPD is the third leading cause of global death (Lancet 2012;380:2095)
- Affects 1.4% of adults in the US (CDC, American Lung Associiation)
- Male : Female = 1 : 0.9
- Usually older than 45 years old
Sites
- Centriacinar emphysema
- Upper lobe predominant
- Respiratory bronchioles and surrounding lung parenchyma
- Panacinar emphysema
- Lower lobe predominant
- Entire acinus
- Paraseptal emphysema
- Upper lung
- Distal part of acinus in subpleural area
Pathophysiology
- Destruction of lung parenchymal tissue due to chronic inflammation
- Protease mediated destruction of elastin is an important feature (Thorax 2016;71:105)
- Morphological progression (Int J Chron Obstruct Pulmon Dis 2016;11:2287, Clin Anat 2015;28:227)
- Increase in size and number of small fenestrae in alveolar walls ("pores of Kohn"), which leads to loss of elastic recoil
- Breakdown and merging of fibrovascular trabeculae ("framework")
- Remodeling of acini results in airspace enlargement
Etiology
- Inhalation
- Cigarette smoking and environmental pollutants, especially for centriacinar emphysema
- However, there is individual susceptibility (Annu Rev Physiol 2014;76:493)
- Infections
- Genetic factors
- Alpha-1-antitrypsin deficiency is well known risk factor, especially for panacinar emphysema (Eur Respir J 2016 Oct 20 [Epub ahead of print], Lancet 2004;364:709)
- Telomerase mutations, especially for CPFE (J Clin Invest 2015;125:563)
- Serpin mutation (BMC Med Genet 2010;11:159)
Clinical features
- Dyspnea; chronic, progressive and usually irreversible
- Chest inflation
- CPFE (Chest 2012;141:222, Eur Respir J 2005;26:586)
- Coexistence of interstitial fibrosis and emphysema of unknown causes
- Patients with CPFE have different pulmonary function tests and outcomes than patients with pure emphysema or pure fibrosis
- Interstitial emphysema (Am J Surg Pathol 2014;38:339)
- Air gains access to the pulmonary interstitium to cause air leak and pneumothorax
- Common in premature infants
- Adults: commonly in usual interstitial pneumonia, but can occur in any interstitial lung diseases
- Bullous emphysema
- Formation of multiple bullae > 1 cm with thin wall
- Can cause bullae inflation and pneumothorax
- Senile emphysema
- Due to age related alteration of acini
- Irregular emphysema
- Occurs in relation to scars
- Congenital lobar emphysema (Pediatr Clin North Am 1994;41:453)
- Hyperinflation of one or more lobes due to malformation of bronchioles
- Causes respiratory distress
- Can be sporadic or caused by autosomal dominant inheritance
Radiology description
- X ray: overinflation of the lung, but it may not be seen in early stages
- Chest CT: emphysematous regions are represented by low attenuation areas (Eur Respir J 2016;48:216)
Prognostic factors
- Based on exacerbation risk of COPD (GOLD)
- GOLD score 3 or 4 (severe or very severe airflow limitation)
- Previous history of exacerbation and hospitalization
- Faster loss of forced expiratory volume in 1 sec
- COPD assessment test score ≥ 10 (CATest, Eur Respir J 2009;34:648)
Case reports
- 18 day old infant with interstitial emphysema (BMC Pulm Med 2016;16:139)
- 31 year old woman with congenital lobar emphysema (Surg Today 2013;43:539)
- 32 year old woman with severe bullous emphysema (Asian Cardiovasc Thorac Ann 2016;24:597)
- 34 year old man and his baby with congenital lobar emphysema (J Pediatr Surg 2002;37:799)
- 65 year old woman with severe emphysema (Clin Respir J 2015 Dec 24 [Epub ahead of print])
- 83 year old man died of CPFE (Int J Chron Obstruct Pulmon Dis 2015;10:1299)
Treatment
- Based on treatment of COPD (GOLD)
- Smoking cessation
- Medications: bronchodilators, antimuscarinic drugs, steroids, etc.
- Ventilatory support
- Surgical interventions: lung volume reduction surgery, bullectomy, lung transplant
- Augmentation therapy for alpha-1-antitrypsin deficiency (Eur Respir Rev 2015;24:46)
Clinical images
Gross description
- Centriacinar: sparse empty spaces with pigmentation (anthracosis) corresponding enlarged airspaces
- Panacinar: airspaces are more or less evenly inflated throughout the secondary lobules
- Paraseptal: inflated subpleural airspaces with thin walls
Gross images
Microscopic (histologic) description
- General findings
- Airspace enlargement; the size of airspace in the background parenchyma will be a good reference
- Fragmented alveolar walls
- If the acinar arrangement is well remained, it is representing pores of Kohn
- If not, it is representing acinar destruction
- Mild fibrotic change can be seen
- Any degrees of inflammation can accompany
- The subtype is determined with histological landmarks:
- Bronchovascular bundle of terminal bronchiole and arteriole is in the center of acinus
- Connective tissue septa ("secondary lobule of Millar") are the periphery of acinus, which is often ambiguous in less inflamed lung
- Note: similar appearance can be seen due to inadequate inflation or fixation of specimen
- CPFE
- Centrilobular emphysema in upper lobes
- Usual interstitial pneumonia in lower lobes
- Interstitial emphysema
- Elongated or angulated spaces in fibrotic interstitium
- Surrounded by dense fibrosis and lining of multiple giant cells, but not epithelium
- Most commonly around bronchovascular bundles
Microscopic (histologic) images
Contributed by Akira Yoshikawa, M.D.
Images hosted on other servers:
Videos
Histopathology Lung - Emphysema
Differential diagnosis
- Interstitial emphysema vs. honeycomb of usual interstitial pneumonia: honeycomb is the air space surrounded by bronchiolar epithelium on fibrotic wall
- Lymphangiomyomatosis: cystic air spaces, proliferation of spindle to epithelioid cells (HMB45+)
- Pulmonary Langerhans cell histiocytosis: stellate nodules with fibrosis and Langerhans cells (CD1a+)