PathCAL Lung Cancer Types Flashcards
From which part of the respiratory tract is a tumour in the lung likely to have originated?
Most types develop in the bronchus; particularly from the bronchial epithelium.
For this reason, lung cancer is often called bronchial carcinoma, or bronchogenic carcinoma
What are the most common types of lung cancer?
- Squamous cell carcinoma
- Small cell carcinoma
- Large cell carcinoma
- Adenocarcinoma
By what structures are the tumour cells in groups attached to one another?
- They’re attached to one another by desmosomes.
- These are dense bodies on the cell membrane that allow tonofilaments to pass from one cell to the other and keep them attached.
- The cells are held together by desmosomal attachments.
If tumour cells are arranged in groups and attached via desmosomes, what sort of neoplasm is it likely to be if malignant?
- It must be a carcinoma. The neoplastic cells must be epithelial.
- If the tumour weren’t epithelial, for example if it were a sarcoma, the cells wouldn’t have desmosomal attachments to one another: their normal counterparts, normal connective tissue cells, don’t have desmosomes.
What is eosinophilic material made of?
- It consists of keratin.
- The keratin is being formed by the neoplastic cells.
- The presence of keratin in a tumour is significant.
Describe the appearance of eosinophilic material
pink-staining material, often arranged in concentric layers to form little whorls
What sort of carcinoma has tumour cells making keratin?
It must be a squamous cell carcinoma.
Other sorts of tumour, such as adenocarcinomas, don’t form keratin whorls like this. So it can’t be an adenocarcinoma.
What sort of epithelium normally lines the bronchi?
columnar epithelium/ pseudostratified columnar ciliated epithelium.
What change occurs in the bronchial mucosa for the development of squamous carcinoma?
Metaplasia
What is metaplasia and what induces it?
Metaplasia is the change from one type of mature tissue to another.
In the bronchus, it’s squamous metaplasia: mature stratified squamous epithelium replaces some of the columnar epithelium in the bronchi.
Metaplasia is a change induced by some alteration in the environment of the cells. Presumably the cells undergo some sort of adaptive change in response. They change to some other cell type.
Describe the early changes in bronchial epithelium leading to cancer
- Confined to the epithelium of bronchial mucosa
- Variation in nuclear size (pleomorphism).
- Disorderly arrangement with respect to one another (dysplasia).
- squamous cells are flattening off towards the surface, although less well than would be normal in, say, the skin or cervix
What do we call a lesion, in which the neoplastic changes are confined to the epithelium and are not yet invasive?
- Carcinoma in situ
- Intraepithelial neoplasia
How do we diagnose squamous cell carcinoma?
- Taking a piece of tissue, called a biopsy.
- Flushing or rubbing off some detached cells, for cytological diagnosis.
What name might we apply to a neoplasm which is so poorly differentiated that we can’t tell what it is?
Undifferentiated/ anaplastic neoplasm
Describe the appearance of an undifferentiated/ anaplastic neoplasm
- are rather smaller than the squamous cells.
- vary in size and shape: they show nuclear pleomorphism.
- are not arranged in groups like those in the squamous carcinoma we saw: this suggests they may not be epithelial.
- do not form keratin: this suggests they aren’t squamous.
- nuclei which stain blue (strongly basophilic)
Why can undifferentiated/ anaplastic neoplasms be classed as carcinoma?
Despite the fact that the cells do not form cohesive groups, it’s possible to demonstrate by immunhistochemical techniques that they express epithelial
antigens. This shows that the neoplasm is epithelial
What cells are small cell carcinomas thought to arise from?
Small cell lung cancer is thought to arise from the neuroendocrine (APUD) cells of the bronchial mucosa, in this site called Feyrter cells.
They’re named after Friedrich Feyrter (1895-1983), who was an Austrian pathologist.
Describe large cell undifferentiated tumours
-Large nuclei, which vary considerably in size (A).
-Nuclei of normal stromal cells for comparison (B). -
-Notice how they’re a lot smaller than the other cells
-Note that we can’t see any evidence of keratin production. For this and other reasons it’s not a squamous carcinoma.
And there’s no sign of gland formation: so it’s not an adenocarcinoma.
What do we see if we examine large cell undifferentiated carcinomas by electron microscopy?
evidence of glandular or squamous differentiation and even neurosecretory granules
What do we call a neoplasm which is forming glands?
Adenocarcinoma
Why is adenocarcinoma different to others?
- Develop in periphery of lung rather than the hilum
- Difficult to biopsy and endoscopy
What are the relative frequency of each neoplasm type?
Squamous= 40%
Small cell= 20%
Adenocarcinoma= 30%
Large cell anaplastic= 10%
How might the frequency of histological types vary?
- Geographical location: the figures differ with country.
- Time: in recent years, for example, the proportion of adenocarcinomas has increased.
- Gender: adenocarcinomas make up a much higher proportion in women.
- Age: adenocarcinoma is more common below the age of 45 years.
How does lung cancer behave?
- Squamous carcinoma tends to spread rather later to the hilar lymph nodes (enlarged at a later stage)
- Small cell cancer responds well to chemo and radiotherapy (targets dividing cells) as it rapidly grows
- Small cell cancer disseminates widely in the body at an early stage
- Squamous carcinoma is treated initially by resecting the primary tumour to debulk it
- Adenocarcinoma is treated first by surgical resection
- Small cell cancer is particularly bad to have as it spreads rapidly
What is a carcinoid tumour?
- Tumour forming groups of cells with dark-staining nuclei
- Tumour contain neuroendocrine granules
- Oid= a bit like so a bit like carcinoma
- relatively small and tend to be located in a main bronchus so often can be resected completely
What is a bronchiolo-alveolar cell carcinoma?
This sort of tumour tends to spread round the walls of the alveoli.
It is, however, forming little glands and so it’s a special type of adenocarcinoma. It’s thought to develop from the small bronchi, called bronchioles, and from the alveolar-lining cells.
How do we categorise biopsies?
- Small cell carcinoma or non-small cell carcinoma
- Small cell= cannot resect, chemotherapy only
Where can metastases of the lung come from?
Stomach
Kidney
Lung
Colon
Which type of bronchial carcinoma is less associated with smoking?
Adenocarcinoma has a less close association with tobacco smoking than the others.
But although it’s found in non-smokers, its incidence in smokers is increased, although less so than the other types of tumour.
How can we overall distinguish the 4 types of lung cancer histologically?
- Squamous cell carcinoma: groups of cells, forming keratin.
- Adenocarcinoma: forms glands, may secrete mucin.
- Small cell carcinoma: cells have small, dark-staining nuclei.
- Large cell carcinoma: cells are large, often with marked pleomorphism.
