usual interstitial pneumonia

Digital cases

 JRC:6098 : Diffuse fibrosing alveolitis.
 JRC:6468 : Usual interstitial pneumonia (UIP).

Images

 UIP usual interstitial pneumonitis / pulmonary fibrosis

• https://twitter.com/UTMBPath/status/745322904552800257
• https://twitter.com/TexPathol/status/849257027348160512

Links

 Usual interstitial pneumonia (UIP) at the Yale Rosen Collection

Definition: UIP, although rare, is the most common of the idiopathic interstitial pneumonias. UIP is considered to be a pathological reaction pattern and not a disease per se.

UIP patterns may be seen in:
 collagen vascular diseases,
 asbestosis,
 drug toxicity,
 chronic hypersensitivity pneumonitis,
 familial idiopathic pulmonary fibrosis,
 the Hermansky-Pudlak syndrome.

The UIP pattern is the underlying pathology in patients with the clinical diagnosis of "idiopathic pulmonary fibrosis" (IPF), also known as "cryptogenic fibrosing alveolitis" (CFA).

Microscopy

 interstitial fibroblastic proliferation
 Scattered chronic inflammatory cells in interstitium.
 There is chronic interstitial inflammation with interstitial fibroblastic activity.
 Restructured airspaces with squamous metaplasia and luminal mucoid secretions are also present.
 There is interstitial chronic inflammation with fibroblastic activity.
 Early collagenous stroma is being formed in interstitial tissue.
 Progression toward a honeycomb remodelling or end stage lung.

UIP is morphologically characterized initially by interstitial inflammation progressing to interstitial fibrosis and ultimately, in some areas, to a drastic revision of the lung architecture known as end stage honeycomb fibrosis.

There are 2 features that are very characteristic of UIP and that are very useful in making a diagnosis.

1) Interstitial fibroblastic foci are circumscribed nodules of fibroblastic proliferation and immature connective tissue. They are rarely seen in conditions other than UIP.

They are qualitatively identical to the Masson nodules seen in organizing pneumonia and the immature fibrous connective tissue seen within alveolar walls and air spaces in organizing diffuse alveolar damage (DAD).

2) Temporal non-uniformity of the lesions.

"Temporal non-uniformity of the lesions" means that lesions of different ages are present.

These may vary from interstitial inflammation only, to interstitial inflammation with fibrosis, to interstitial fibrosis without inflammation and to end stage honeycomb fibrosis.

Spared areas of lung tissue are also seen.

Temporal non-uniformity seems to indicate that the agent of injury has acted in an episodic manner over a prolonged period of time.

Synopsis

 areas of varying appearance with areas with relatively normal alveoli and areas with interstitial fibrosis and interstitial inflammation.
 interstitial fibroblastic proliferation
 fibroblastic foci
 dense consolidation
 "temporal non-uniformity" : lesions of differing ages
 prominent fibroblastic foci with adjacent areas of dense consolidation
 relatively early lesion exhibiting interstitial inflammation without fibrosis
 Scattered chronic inflammatory cells in interstitium.
 Interstitial fibrosis and mild inflammation.
 There is chronic interstitial inflammation with interstitial fibroblastic activity.
 Restructured airspaces with squamous metaplasia and luminal mucoid secretions are also present.
 There is interstitial chronic inflammation with fibroblastic activity.
 Early collagenous stroma is being formed in interstitial tissue.
 Progression toward a honeycomb remodelling or end stage lung.

 Several well-defined nodules of immature connective tissue with fibroblasts.

• These lesions are called "fibroblastic foci".
• They are a characteristic finding in UIP and are rarely seen in other forms of idiopathic interstitial pneumonia.
• Their presence in UIP is indicative of ongoing disease activity.
• The tissue comprising these nodules is identical to the intraalveolar Masson bodies seen in organizing pneumonia and to the intraaeveolar fibroblastic proliferation seen in the organizing/proliferative phase of diffuse alveolar damage (DAD).
• well-defined nodules of immature connective tissue with fibroblasts, called fibroblastic foci.
• They are a characteristic finding in UIP and are rarely seen in other forms of idiopathic interstitial pneumonia.
• Their presence in UIP is indicative of ongoing disease activity.
• The tissue comprising these nodules is qualitatively identical to the intraalveolar Masson bodies seen in organizing pneumonia and to the intraaeveolar fibroblastic proliferation seen in the organizing/proliferative phase of diffuse alveolar damage (DAD).
• fibroblastic focus in the midst of interstitial fibrosis.
• collagenization of interstitial fibrosis

 Interstitial fibroblastic foci are circumscribed nodules of fibroblastic proliferation and immature connective tissue.

• Fibroblastic foci, consisting of proliferation of immature fibrous connective tissue at the periphery of an air space, are a characteristic finding in UIP and are indicative of disease activity.
• They may sometimes be found in other types of interstitial pneumonia.
• Temporal heterogeneity, patchy low power appearance and fibroblastic foci are important diagnostic features of UIP.

 Temporal non-uniformity of the lesions means that lesions of different ages are present.
 marked alveolar wall expansion by fibroblastic proliferation and immature connective tissue
 honeycomb fibrosis;

• spaces lined by respiratory epithelium separated by thick bands of mildly inflamed fibrous connective tissue and smooth muscle.
• These spaces are mostly dilated terminal airways;
• some are alveoli with a metaplastic epithelial lining.
• This type of lung tissue is incapable of performing the gas diffusion function of the lung.
• spaces lined by respiratory epithelium separated by thick bands of mildly inflamed fibrous connective tissue and smooth muscle.
• These spaces are mostly dilated terminal airways; some are alveoli with a metaplastic epithelial lining.
• spaces lined by respiratory epithelium separated by thick bands of mildly inflamed fibrous connective tissue and smooth muscle.
• These spaces are mostly dilated terminal airways; some are alveoli with a metaplastic epithelial lining.
• spaces lined by respiratory epithelium separated by thick bands of mildly inflamed fibrous connective tissue and smooth muscle.
• These spaces are mostly dilated terminal airways; some are alveoli with a metaplastic epithelial lining.
• This type of lung tissue is incapable of performing the gas diffusion function of the lung.
• CT scan: There is interstitial thickening, architectural distortion, honeycombing and bronchiectasis.
• Macroscopy: Dilated spaces separated by thick bands of fibrous connective tissue and resembling a bee’s honeycomb.
• Honeycomb lung is a common end stage of many types of chronic fibrosing interstitial lung diseases.

 spaces lined by respiratory epithelium separated by thick bands of mildly inflamed fibrous connective tissue and smooth muscle.

• These spaces are mostly dilated terminal airways;
• some are alveoli with a metaplastic epithelial lining.
• This type of lung tissue is incapable of performing the gas diffusion function of the lung.

References

 Interobserver Agreement of Usual Interstitial Pneumonia Diagnosis Correlated With Patient Outcome. Hashisako M, Tanaka T, Terasaki Y, Uekusa T, Achcar RD, Aswad BI, Bamefleh HS, Capelozzi VL, English JC, Fabro AT, Kataoka K, Hayashi T, Kondoh Y, Taniguchi H, Fukuoka J. Arch Pathol Lab Med. 2016 Sep 9.
http://dx.doi.org/10.5858/arpa.2016-0012-OA

 Usual interstitial pneumonia: histologic study of biopsy and explant specimens. Katzenstein AL, Zisman DA, Litzky LA, Nguyen BT, Kotloff RM. Am J Surg Pathol. 2002 Dec;26(12):1567-77. PMID: 12459623