What is Type 2 Pneumocyte hyperplasia?

In summary, prominent type 2 pneumocyte hyperplasia can occur in the settings of spontaneous pneumothorax and, similarly to other reactive processes such as squamous metaplasia, can mimic epithelial malignancy in the lung.

What is reactive Pneumocyte hyperplasia?

Reactive Pneumocyte Hyperplasia: This lesion is usually seen in the setting of parenchymal inflammation or fibrosis. AAH is rarely accompanied by interstitial fibrosis or inflammation.

What is a Type II Pneumocyte?

Type 2 pneumocyte: The cell responsible for the production and secretion of surfactant (the molecule that reduces the surface tension of pulmonary fluids and contributes to the elastic properties of the lungs).

What does Type II Pneumocyte damage cause?

Injury to the type II pneumocytes can reduce the production of surfactant, which contributes to the clinical course of worsening atelectasis and gas exchange. The process of epithelial repair is usually inadequate, leading to fibrosis (Zapol et al., 1979a).

Can type 2 pneumocytes regenerate?

Type II epithelial cells are small cuboidal cells which usually reside in the corners of the alveolus, covering roughly 2% of the alveolar surface area. Type II pneumocytes are known to produce surfactant and regenerate alveolar epithelium after injury.

What are the causes of type II Pneumocyte hyperplasia?

CAUSES OF TYPE II PNEUMOCYTE HYPERPLASIA: pneumonia. sepsis (diffuse alveolar damage) pulmonary embolus with infarction.

What are reactive pneumocytes?

Various types of acute and subacute lung injury can cause severe reactive pneumocyte atypia, which may mimic malignant proliferations and present a major diagnostic pitfall. This particularly applies to cytologic preparations and frozen sections, where background inflammatory injury may be subtle or not apparent.

What is the function of Pneumocyte Type 2?

The main function of type 2 pneumocytes is the production of pulmonary surfactant: Surfactant is a complex mixture of phospholipids (mainly dipalmitoyl phosphatidylcholine), carbohydrates (glycosaminoglycans) and proteins (including SP-A, SP-B, SP-C and SP-D)

How would you tell the difference between type I and type II cells?

The type I cell is a complex branched cell with multiple cytoplasmic plates that are greatly attenuated and relatively devoid of organelles; these plates represent the gas exchange surface in the alveolus. On the other hand, the type II cell acts as the “caretaker” of the alveolar compartment.

Are Clara cells type II pneumocytes?

These cells were first recognized as a distinct cell type based on morphology and histochemistry in 1881 by Kölliker (1). In 1967, Niden suggested that Clara cells secrete pulmonary surfactant and that the lamellar bodies seen in alveolar type II pneumocytes represented phagocytized surfactant (4).

When do type 2 pneumocytes secrete surfactant?

Surfactant Inactivation Surfactant is a macroaggregate molecule secreted by type 2 pneumocytes as the infant approaches term gestation. Surfactant is made up of 90% phospholipid and 10% proteins (surfactant protein [SP] A, B, C, and D). The primary function of surfactant is to reduce surface tension in the lung.

What are Type 3 cells?

The type III cell has two distinctive features that are not present in other lung epithelial cells: a microvillous brush border and bundles of fine filaments. Regarding its topography, the cell appears to have a preferential although variable localization in different species.

When does type 2 pneumocyte hyperplasia occur?

Type 2 pneumocyte hyperplasia is a universal reaction in injured lung. 3, 14 It is most striking in diffuse alveolar damage (DAD), but is also seen in organizing pneumonia, non-specific interstitial pneumonia, and in a variety of other settings, including acute bronchopneumonia, in the lung surrounding granulomas,…

Which is the most reactive type of pneumocyte?

Pneumocytes are reactive with type II pneumocyte hyperplasia and accompanying interstitial and intra-alveolar edema with paucicellular inflammation. From: Murray and Nadel’s Textbook of Respiratory Medicine (Sixth Edition) , 2016

What kind of nodules are in adenomatous pneumocyte hyperplasia?

Composed of multiple nodules of enlarged but benign type II pneumocytes that may mimic atypical adenomatous hyperplasia Older terminology: acinar atypical adenomatoid proliferation of epithelium, multiple adenomatoid lesions, micronodular hyperplasia of type II pneumocytes

Which is type 2 pneumocytes are immunoreactive with TTF 1 h?

Hyperplastic type 2 pneumocytes of the lesion are immunoreactive with TTF-1 ( H ), × 200.