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Flashcards in Pulmonary Pathology 2 Deck (29)
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How does diffuse alveolar hemorrhage look in histology?

- Blood and iron-containing macrophages in airspaces

- Alveolar septa thickened by inflammation and fibroblasts

- May be associated with capillaritis


How can you tell that this is actual alveolar hemorrhage and not blood from the biopsy process?

You look for macrophages that are iron-containing (look brownish yellow). Also, the presence of the immune response tells you that it's alveolar hemorrhage and not just from the biopsy.


How can you tell if diffuse alveolar hemorrhage is associated with capillaritis?

Capillaries are difficult to visualize in histology, especially when there are neutrophils all over the place. So, when there are neutrophils along the alveolar septa with diffuse alveolar hemorrhage, it is assumed that they are attacking the capillaries and causing hemorrhage (autoimmune).


This is important to distinguish because autoimmune causes of disease are treated differently.


What is pulmonary alveolar proteinosis and how does it look in histology?

Pulmonary alveolar proteinosis is the presence of proteinacious fluid in alveolar spaces.

In histology, you get airspaces filled by pink fluid and macrophages.

The pink color of the fluid suggests that there is protein in the fluid. Unlike in alveolar hemorrhage, the septa do not thicken.


What is usual interstitial pneumonia and how does it appear in histology?

Usual interstitial pneumonia (UIP) is a form of lung disease characterized by progressive scarring of both lungs. It is the most common form of interstitial fibrosis.

Idiopathic pulmonary fibrosis almost always presents with this pattern.

In histology, UIP has patchy heterogenous fibrosis by collagen, fibroblastic foci, and honeycomb cystic changes.

You can see in the picture that different parts are at different stages of the disease process.


What's this?

Fibroblastic foci


What is honeycombing? Which lobes have the worst honeycombing?

It is the latest stage of fibrosis. The lower lobes have the worst honeycombing. (we don't know why)


What's going on here?



What does Nonspecific interstitial pneumonia look like in histology?

- uniform inflammation in septa (cellular)

- uniform fibrosis of septa (fibrotis)

- or both (mixed)

Few if any fibroblastic foci and little if any honeycomb change. Think of nonspecific interstitial pneumonia (NSIP) as the opposite of usual interstitial pneumonia (UIP) in histology pattern.


What's going on here?

This is cellular nonspecific interstitial pneumonia (Cellular NSIP).


You can tell it's cellular because there are cells, not fibrosis, expanding the septae. This disease is treatable if you can get rid of the inflammatory cells (better prognosis than fibrotic NSIP).


What's going on here?

Fibrotic non-specific interstitial pneumonia (Fibrotic NSIP)


What's going on here?

Mixed non-specific interstitial pneumonia (mixed NSIP)


How does hypersensitivity pneumonia look in histology?

Hypersensitivity pneumonia is a response to foreign antigens (birds, mold, hot-tub mycobacteria, etc). It is more severe in the upper lobes (just like smoking. almost anything inhalational is worse in the upper lobes)

- Airway-centered chronic inflammation

- Non-necrotizing granulomas (poorly formed)

- Focal organizing pneumonia

- Variable fibrosis


What's this?

Nonnecrotizing (poorly formed) granuloma.


In sarcoidosis, the granulomas look very circular and encased. This one is not well-formed so it is a sign of hypersensitivity pneumonia (trying to engulf foreign antigenic material)


True or False: Hypersensitivity Pneumonia can cause scarring that doesn't go away.

True. In the picture, you can see the multinucleated giant cells embedded in the scarring.


How does thromboembolic disease look in histology?

Organizing fibrin clots in pulmonary arteries. May be in situ (thrombus) or travel to the lung from elsewhere (embolism)


It's called thromboembolic disease because we can't tell the difference between if it is in situ or if it's from elsewhere--the histology looks the same.


Talc embolism is seen most often in what kind of patients?

IV drug users


How does talc embolism look in histology?

Polarized crystals around vessels

May include foreign-boy multinucleated giant cells

Typically from IV drug use


How does pulmonary hypertension look in histology?

- Muscular hypertrophy of pulmonray arteries

- Muscularization of arterioles (arterioles should not have muscle)

- Some forms may have plexiform lesions (artery lumen replaced by endothelial proliferation with numerous tangled slit-like lumens)


What's going on here?

Muscular hypertrophy of the pulmonary artery which suggests pulmonary hypertension


What is this?

This is muscularization of an arteriole. Arterioles definitely shouldn't have this much muscle. This suggests severe pulmonary hypertension


What's going on here?

This is plexiform lesion which suggests pulmonary hypertension.

It is a proliferation of endothelial cells and smooth muscle cells which makes a tangled web of spaces. 


How does vasculitis look in histology?

Inflammation in the vessel wall often with alveolar hemorrhage (may be autoimmune or due to infection).




How does sarcoid and chronic beryllium disease look in histology?

Well-formed non-necrotizing granulomas

Concentric collagen deposition

Lymphatic distribution (near vessels, airways, and pleura).


Sarcoid and chronic bryllium disease look identical in histology. The difference must be determined from history of exposure.


How does pulmonary langerhans' cell histiocytosis (PLCH) appear in histology?

PLCH is related to smoking and it causes more disease in the upper lobes.

Cellular phase (when the disease is active):

- Langerhans' histiocytes (CD1a/S100 positive).

- Variable inflammation including eosinophils (sometimes no eosinophils)

Fibrotic phase:

- stellate scar around airway


On the left is the cellular stage and on the right is the fibrotic phase.


How does carcinoid appear in histology?

The lung is prone to form carcinoid (neoplasm that isn't benign but often behaves in a benign way).


- Nests and ribbons of neuroendocrine cells with powdery salt-and-pepper chromatin.

- Stain positive for neuroendocrine markers (chromogranin, synaptophysin, CD56)


*Note it's hard to read this histology but staining for the markers helps


How does small cell carcinoma look on histology?

Small blue easily-crushed cells with scant cytoplasm.

They stain positive for neuroendocrine markers (chromogranin, synaptophysin, and CD56).

High mitotic rate and abundant necrosis.

It is believed that small cell carcinoma comes from same progenator as the carcinoids (so similar cells are present).


On the left, you have an example of the crushed small cells where the material can be barely made out and looks squished by neighbors.

On the right, you have small blue cells with very little cytoplasm.


How does squamous cell carcinoma look in histology?

Large polygonal cells with hyperchromatic (dark) nuclei and abundant cytoplasm.

Rarely have prominant nucleoli.

May be keratinizing and form "keratin pearls".


When you see islands of these cells (in the picture on the left) where they don't belong, think squamous cell carcinoma. On the right, you see a keratin pearl which only show up with squamous cell carcinoma. The cells are pushing keratin into the center into a pearl.


How does adenocarcinoma look in histology?

Cells with large nuclei, large nucleoli, and variable amounts of cytoplasm.

Form gland-like structures.


When you see islands of cells trying to make glands, you know it's adenocarcinoma



How does large cell carcinoma look in histology?

Large, sometimes bizarre-appearing malignant cells that lack the typical features of either adenocarcinoma or squamous cell carcinoma.