For years it was treated as a one-off lump which could be cut or make you write off the person who had it entirely. We knew very little beyond the fact it was nasty, so we didn't look at it too closely and kept our fingers crossed.
Then as we realised it was touching many people we took a closer look, and now we know how it starts, the symptoms, and more importantly than anything else that it can spread through your cells like liquid mercury and produce a problem somewhere unexpected.
And because we know more about it, we're better at tackling it. We don't need to keep our fingers crossed when our doctors have the best chance they've ever had to hunt it down and kill it without killing us too.
The same is true of child abuse.
We all grew up not knowing much about it, blaming it on the occasional 'dirty old man' we avoided out of instinct rather than any kind of knowledge.
It wasn't an offence that was easy to prosecute because the law used to insist on a third-party eyewitness, and because of that and the fact The Reader just didn't want to know, newspapers didn't report on it much.
Sexual assault laws have changed, people are more likely to come forward now and juries are more able to weigh up the facts. But it's often many years after the event, by which point the human tumour you're trying to put behind bars is beyond offending and has already done so much damage lives have long been ruined.
They're a manipulative, twisting, lying lot, child abusers, and like an ever-mutating cancer they're hard to pin down and examine. It takes money and time and effort, so few people go to the trouble.
But they're are not isolated cases. A parent who abuses their children will claim to have been abused themselves, and whether that is true or an attempt at sympathy we don't know because we don't care to look too closely.
What if child abuse is not one lump that can be easily cut out, but a chain that needs to be traced back to the source? Cutting out one link is not going to do much - it just creates two chains.
In the past few weeks the nation has been horrified, disgusted and then steadily bored by revelations of a children's TV presenter abusing youngsters from hospitals, mental hospitals, children's homes, and special schools.
And we've treated Jimmy Savile like he's one lump, now thankfully dead, who we can dissect a little and whinge about why we weren't able to spot him earlier and who should have told us sooner.
But it suddenly seems like there a lot of suspicious bumps, and most of them seem to be under the carpet.
Yesterday an MP claimed that a investigation into a man convicted of importing child porn - and who was a member of a group which campaigned for the age of consent to be reduced to four years - contained a number of leads which were not followed up.
That's like finding a cancer, seeing it leads somewhere else in the body, and not having a root around.
The leads included claims an aide to a former Prime Minister could provide pornographic pictures of children. The man who was convicted had also been in a relationship with the headteacher of a school for disturbed children, and we don't know if that was looked into either.
Sir Peter Morrison, a former aide to Margaret Thatcher, was this weekend revealed to have received a caution for cottaging with under-age boys. He was picked up twice, but due to his position as deputy chairman of the Conservative party never charged with gross indecency with children. Police officers tipped off a reporter (pay attention, Sue Akers and Brian Leveson) whose story was blocked by Morrison's abuse of the libel laws.
The long-dead PM Edward Heath is the subject of unsubstantiated rumours about paedophilia aboard his yacht, and an alleged friendship with Jimmy Savile who he awarded an OBE to in 1971 for services to charity which, in all fairness, had barely begun.
One person has even made allegations against a serving Cabinet minister. It may be completely untrue, but the minister is unable to defend themselves just as much as their accuser is unable to openly accuse.
The lumps may all be unconnected, but seeing as they're under the same carpet it's worth lifting for a look, don't you think?
The trouble is there are a lot of people standing on it and telling you there's no point. The Prime Minister and Director-General of the BBC say the three internal management reviews the corporation is holding are 'independent' and need to be 'allowed to do their job'.
After which, they will report to the BBC management. Not to us.
A Government minister stopped from raising the allegations during an appearance on the nation's prime political debate programme tried to present it as evidence of a cover-up to one of those reviews, only to be told it 'was not considering evidence from external sources'.
So a review into a possible cover-up at the BBC is only considering evidence from the BBC. I wonder what would have happened if the News of the World had tried that.
I also wonder what would happen if, during the course of those reviews, they accepted evidence from convicted child rapists. You'd think there'd be a fuss, although when Jonathan King claimed the Press had got him wrongly jailed at an Establishment-led inquiry he was listened to carefully.
It's all incredibly distasteful, and there are many when faced with grime who'd rather not look under the carpet at all and hope that's where it stays.
But the NSPCC has 161 allegations against Savile. The BBC has several allegations made about other stars. Downing Street questions to answer about at least one former member of staff. NHS doctors have been named, and former Health Minister Edwina Currie for some reason let Jimmy Savile take over Broadmoor in the 1980s. There are wild rumours flying about people living and dead, in positions of great power, which nobody knows to be true or false.
It is also the case that you do not need to do much more than call someone a paedophile to have them forever tainted as such, even if they are innocent. Imagine the fear some people must feel that false allegations may be made by damaged people, which unlike every other crime needs you to prove your innocence before anyone will believe it to be true.
Perhaps all those lumps under the carpet are unconnected. Maybe we'd all rather not look. But it's undeniably a hell of a mess and the only thing which has a hope of cleaning it all up is a proper investigation capable of following the evidence wherever it leads and letting everyone have their say.
If there is no public inquiry set up by the Government, the public will hold their own via the newspapers. Now that we know there's something amiss other victims will come forward because when denied justice everywhere else the court of public opinion is an effective last resort.
There is more smoking here than Jimmy Savile's manky cigar. We can all smell it, and it is far better to find out it's a weird one-off rather than a bloody great cancer galloping through our guts we've been ignoring the symptoms of for far too long.
And if it is a tumour with tendrils extending into all our institutions - let's blast it with something.
Sweep it up, or be swept aside.