What is cancer?
Cancer is defined as a group of cells which divide uncontrollably and consequently wreak havoc within the body and refuse to cooperate with the body’s natural defences. It’s not to be confused with the sun sign Cancer which is a crab. Actually, the crab is a good analogy for a malignant cancer cell; as the picture above demonstrates, malignant cells tend to protrude outside of their natural boundary, and if left unchecked, they can enter the bloodstream and form cancers in other parts of the body. This process is known as metastasis, and often the prognosis is poor for patients that have cancers which have spread away from their original source. I’ll discuss the metastatic process in more detail in Metastasis.
But wait… aren’t benign tumours also considered as cancer?
It is true that benign tumours are often referred to as cancers, but what I was taught in my histopathology classes at university was that the term ‘cancer’ is only used for malignant tumours. Benign tumours tended to be referred to as tumours in order to avoid confusion. I’ll discuss the differences between benign tumours and malignant cancers further in Benign vs Malignant Tumours.
If I hear a doctor mention a name of a type of cancer, how do I know if it is a bad one or not?
All cancers are bad in their own way, but some are definitely worse than others. The prognosis of the patients can vary significantly, depending on when the cancer is detected and where it is located within the body. A hint to determine whether the cancer is malignant is to listen out for the suffixes‘-sarcoma’ or ‘-carcinoma’. If this suffix is at the end of the name, it is definitely malignant. Depending on the location though, it may or may not require chemotherapy. Basal cell carcinomas for instance, are usually located in the one area on the skin and can be excised surgically without the need for chemotherapy. Usually, benign tumours have the suffix ‘-oma’ on the end of them, they can include adenomas, fibromas and meningiomas.
How are tumours detected under the microscope?
After a biopsy is taken, the sample gets taken to the histopathology lab. At the lab, the sample is then put through paraffin processing, is cut up with a microtome and then stained with H&E (haematoxylin and eosin) stain. This process is done regardless of whether a tumour is suspected to be in the tissue sample or not.
Why is the sample placed in paraffin wax? What is so special about it?
The properties of paraffin wax which allows it to be the ideal medium to place tissues in are the following:
- At room temperature, it is solid, but it has a low melting point, which means it can be used without causing burns
- It is quite solid at room temperature, which makes it ideal for cutting into very small slices without warping the tissue structure, but it is also malleable when it is molten
- It is quite easy to remove before staining begins: it is removed by using a combination of xylene and differing degrees of alcohol.
Why is H&E staining used for histopathology?
Pretty much every sample that gets taken through the histopathology lab receives a H&E stain on one of their slides. It is the ideal stain for examining the structure of the tissue you are looking at, as the purple haematoxylin attaches to the nuclei of the cells, and the pink counterstain eosin stains different parts of the cytoplasm, as the picture of the intestine alongside demonstrates.