Men who regularly check their testicles for lumps could spot cancer before it becomes severe.
More than 2,000 men are diagnosed with testicular cancer every year in the UK, with the risk highest among those aged 30 to 34.
While mammograms and cervical screenings help identify common tumours in women, testicular cancer has no national screening programme, making it all the more important that men get a handle on what is normal for them.
Testicular cancer is one of the most treatable forms of the disease, with nearly all (98%) patients surviving at least five years post-diagnosis in England and Wales.
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Nevertheless, the tumour spreads in around 5% of cases, which often requires more aggressive treatment than the go-to surgery.
Spotting the disease before it becomes advanced could help a patient avoid chemotherapy, preserve his fertility and even save his life.
A 2019 study of more than 2,500 men found over three in five (62%) of those aged 18 to 34 were in the dark about how to check their testicles. Just under a third (28%) had not examined their testicles in the past year.
The NHS stresses men should "be aware of what feels normal" for them. "Get to know your body and see a GP if you notice any changes," it adds.
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A painless lump or swelling in one or both testicles can be a tell-tale symptom.
Testicular lumps are relatively common, often coming about due to swollen blood vessels or cysts in the tubes around the testicles.
Although rarely caused by cancer, any swelling should always be checked by a GP.
"Performing a self-examination is as simple as rolling one testicle between [the] thumb and fingers, and feeling for what's normal for you," Sam Gledhill, Movember's global director of testicular cancer, told Yahoo UK.
"Repeat this technique with the second testicle.
"If something changes, starts to hurt, wasn't there before or generally worries you, please don't panic, but do get in front of a doctor and discuss it with them."
Cancer can also cause the testicles to change shape or texture, or feel unusually firm or heavy. One may also look different to the other.
A dull ache or sharp pain, which may come and go, should also raise alarm bells.
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Cancer survivor Stewart Morgan told Yahoo UK he felt "real discomfort" in his right testicle while leaning against a bathroom sink.
The student, 22, then examined his testicles in the shower, discovering a "pea-sized lump" that was "as hard as a snooker ball".
Speaking this Testicular Cancer Awareness Month, Gledhill is encouraging men to #knowthynuts by examining themselves in the shower around once every four weeks.
The bathroom's steamy environment "helps the testicles to relax, creating the right conditions to feel around for anything out of the ordinary", he said.
Amid concerns many – particularly men – may literally be dying of embarrassment, Gledhill has stressed medics have seen it all before.
"We can almost guarantee your doctor has seen many testicles before and no question is a stupid one when to comes to your health," he said.
"In most cases, the outcome for men with testicular cancer is positive, however, early detection is key."
Watch: Actor Colin Egglesfield opens up about his testicular cancer