Beloved Australian actor, Magda Szubanski, has revealed she's been diagnosed with a "very rare, very aggressive, very serious" blood cancer called mantle cell lymphoma.

In a post on social media on Thursday, Szubanski said she would be starting treatment in a few weeks for the stage 4 cancer, which she called "one of the nasty ones, unfortunately".

So, what is mantle cell lymphoma? And how is it treated?

There are more than 100 subtypes of blood cancers, but they are commonly divided into one of two groups. These are based on where they originate: leukaemias develop in the bone marrow, and lymphomas develop in the lymphatic system.

Lymphomas develop from white blood cells (lymphocytes), which circulate in the blood and lymphatic system and help fight infection.

You may not have heard of the lymphatic system, but it plays a key role in your immune response.

The lymphatic circulatory system is responsible for transporting fluids (lymph) around your body. Lymph comes from blood plasma, and helps remove waste from your tissues.

As part of the lymphatic system, tissues like the spleen and thymus help produce many of the immune cells you use to fight infections.

These cells are then housed in specialised organs called lymph nodes - small pea-sized glands located throughout your body.

Lymph nodes are kind of like the "war room" of your immune system.

Your body contains hundreds of lymph nodes, and each contains millions of lymphocytes. These include the T and B cells - the main fighting cells in adaptive immunity.

If B cells in an area of the lymph node known as the "mantle zone" become cancerous, it is called mantle cell lymphoma.

In 2020, there were 330 cases of mantle cell lymphoma diagnosed in Australia, accounting for a small fraction (5%) of lymphoma cases.

Overall, lymphomas account for around one in twenty new cancer diagnoses. This makes mantle cell lymphoma quite rare.

Mantle cell lymphoma is about three times more common in men than in women, and mostly affects people over the age of 60.

Unfortunately, mantle cell lymphoma is largely considered incurable with the therapies currently available.

Like many cancers, mantle cell lymphoma can vary in how quickly it develops and its severity.

As Szubanski's cancer has been described as "fast-moving" and is already stage 4, it appears that it is a more serious case.

Stage 4 is the most advanced stage - meaning the cancer has spread (metastasised) to other tissues.

Treatment at this stage can be more complicated than when the cancer is caught earlier. But treatment can still help people go on to live for many years.

In her social media post, Szubanski said she will be receiving "one of the best treatments available (the Nordic protocol)".

This is one of the most common treatments for an aggressive lymphoma.

The main component is "R-CHOP" - a combination therapy. It involves a mixture of different drugs, including chemotherapy, to attack the cancer from multiple angles at the same time.

Different strengths of the drugs can be used (the maximum strength is sometimes called R-maxi-CHOP).

A stem cell transplantation may also be included in the regimen.

How effective this treatment is will depend on many different factors, including the type and stage of the lymphoma.

The aim is to kill as many cancer cells as possible, and therefore extend a patient's life for as long as possible.

Therapy also focuses on providing a high quality-of-life for patients.

Szubanski's mantle cell lymphoma was detected during a breast cancer screen where, she says, "they found my lymph nodes were up".

Imaging techniques, such as a mammogram or MRI, may detect tell-tale signs of lymphoma, such as swollen lymph nodes.

However a biopsy - a small sample of tissue from the affected area - would then be required to confirm the presence of cancer cells and identify what type.

Blood cancer symptoms can be vague, but it's good to know what to look for.

As well as swollen lymph nodes, symptoms of lymphoma include nausea, tiredness, loss of appetite, fevers, gastrointestinal issues, unexplained weight loss, and night sweats.

If you have any concerns, you should consult a doctor.