There are over 200 different types of cancer in total, and more than one in three people will develop some form of the condition during their lifetime, so it's important to be clued-up on the potential warning signs that something isn't quite right.
Where it gets tricky, though, is when those warning signs aren't exactly obvious.
Most of us know to get any unusual lumps checked out by a doctor, but there are several other more subtle, or less talked-about, symptoms that are just as important to know about - many of which we often easily brush aside and ignore.
Treatments work best when cancer is caught early, so noticing any unusual changes - and getting them checked out - sooner rather than later can make all the difference to your health. Remember, most of the time, these 'symptoms' will turn out to be entirely harmless and don't automatically mean you have cancer, but it's always best to get them seen by a doctor and talk through your concerns.
Here, medical experts explain more about some of the red flags that many people overlook ...
1. Unexplained weight loss
Dropping a dress size might seem like good news at first, but if you haven't made any significant changes to your diet or exercise routine, it could be a sign that something is wrong. "Many different cancers cause weight loss," says Dr Clare Morrison, speaking on behalf of MedExpress (medexpress.co.uk). "This is because tumours use up a lot of energy and nutrition as they grow." Small fluctuations in weight are normal, and it's not uncommon for a noticeable change in your size to happen after a stressful event - but unexplained significant weight loss should never be ignored.
"Many people with cancer experience weight loss at some point, but it occurs most often with cancers of the stomach, oesophagus, pancreas or lung," says Dr Tim Woodman, medical director at Bupa UK (bupa.co.uk). If you're struggling to put any lost weight back on, speak to your GP, as they will be able to rule out any serious illnesses.
2. Ongoing tiredness
We all have those days where we can't seem to keep our eyes open at our desk, and if your lifestyle is particularly demanding and you're not getting enough sleep, then it stands to reason that you're going to feel tired. But unusual exhaustion that's been going on for a while, could be due to something else going on beneath the surface. "Fatigue can be an early sign of cancer; a continuous feeling of exhaustion that doesn't get better even after you rest," says Dr Jan Schaefer, chief medical officer at Medigo (medigo.com). "This symptom is relatively easy to miss, especially if you lead a busy lifestyle."
Often, fatigue occurs in the early stages of cancer because of blood loss in the body. "Cancers of the digestive tract tend to cause internal bleeding," says Dr Morrison. "While the blood loss may be too subtle to notice in one's faeces, it may gradually lead to anaemia. The first sign of this may be fatigue and exhaustion, as well as shortness of breath, palpitations and ankle swelling."
3. Unexplained or irregular bleeding
Both women and men can experience this, explains Dr Schaefer. "If a woman bleeds 12 months after menopause, it's a worrying sign - no matter if the bleeding is light or not - as it could signify cervical or endometrial cancer."
Irregular periods and bleeding between cycles, or after sex, can also be a cause for concern in younger women, but this could also be indicative of other health problems or hormonal fluctuations. As before, it's always best to go and see your doctor as soon as possible, and let them decide if further investigations are needed. Additionally, rectal bleeding shouldn't be ignored. "While it's most commonly linked to a haemorrhoid, rectal bleeding with dark blood should be enough of a concern to make a trip to the GP," adds Dr Schaefer.
4. Swelling in the neck
Medical advice says that we should regularly check our breasts and testicles for any errant lumps or bumps, but your neck could also be a key indicator of cancerous cells. "Many patients don't realise the significance of a persistent neck lump, and leave it too long before seeing a doctor," warns Dr Morrison. "It is a worrying symptom, as it can signify a tumour anywhere in the head or neck, including cancer of the mouth, throat, ear, sinuses, larynx (voice box) or thyroid."
She explains that neck growths can also be a sign of blood cancer and lymphoma: "Neck swellings are common with viral infections, but these usually settle down within a couple of weeks. If a swelling persists for six weeks or more, they should be examined by a specialist."
5. Mouth ulcers that don't heal
A mouth ulcer is a pretty run-of-the-mill complaint, which should clear up on its own within a week or two. If an ulcer's causing discomfort for more than three weeks, however, or you're getting lots of stubborn ulcers, it could be a sign of something more serious going on.
"Many of us experience mouth ulcers when we're a bit run down and our immune system is weakened," says Dr Schaefer. "The lining of the mouth renews itself every two weeks, which usually helps any ulcers heal themselves. So if you're experiencing persistent ulcers for over three weeks, make sure to seek medical advice."
6. Persistent bloating
Many of us will feel bloated after a big meal, but if you feel bloated every day (even if it comes and goes) then this could be a sign of something more than just a heavy dinner or a food intolerance. "If you persistently feel bloated for three weeks or more, it's best to visit your doctor," says Dr Woodman. "The same goes for feeling full quickly, or loss of appetite."
7. Changes in bowel habits
Our bowel patterns can tend to vary from day to day, depending on what we've eaten or how stressed we are. However, any ongoing usual pattern changes, particularly if you are producing more frequent, smaller stools, like pellets or pencil-thin motions, could indicate bowel cancer.
Dr Morrison explains that other symptoms may include rectal bleeding, weight loss, fatigue, abdominal pain and/or swelling, or a feeling that the bowels aren't emptying fully: "Bowel cancer is one of the most common types of cancer, yet it often causes no symptoms until it has progressed to a large tumour. The earlier it is diagnosed, the better the prognosis, so these symptoms should always be taken seriously."
8. Non-healing skin blemishes
Skin blemishes occur in various shapes, sizes and colours, and can appear on the skin at any time in life. "People often overlook small non-healing blemishes on the skin. It's easy to see why this is, as when we age, there are many different spots and marks on the skin and it's difficult to distinguish between the innocent ones and the potentially harmful ones," says Dr Morrison.
"As a rule, if a mole enlarges, gets darker, has an irregular outline, or uneven levels of pigmentation, then it should arouse suspicion of malignant melanoma, a serious form of skin cancer. (But also) any blemish that bleeds, gets scabby, ulcerated or fails to heal, should also be shown to a doctor."
9. Unexplained pain
A crick in the neck, an ache in the lower back - everyday aches and pains are common and usually nothing serious, so it's very easy for people to overlook this potential symptom. But any ongoing pain, anywhere in the body, that doesn't seem to have an obvious cause or doesn't go away, should be checked out.
"Pelvic pain may mean ovarian cancer; back pain may be caused by secondaries from an unnoticed tumour elsewhere, such as breast or prostate; abdominal pain may be caused by cancer of the stomach, bowel, or pancreas to name a few examples; and chest pain may indicate lung cancer," says Dr Morrison.
"Any unexplained pain, particularly if new, persistent, constant, disturbing sleep, or associated with weight loss, should be brought to the doctor's attention."