I see at most one person before your post. And even they were saying it seems more likely, not that it must be.
That is not how statisics and probability work.
The instances may be 0, 0, 0, 0, 2, 0, 5, 5, 5, 5, 0, 12, 11, 1, 0, 0, 0. For no particular reason. It does not mean that anything is causing this.
Yeah, but “It’s a remote statistical possibility that something weird is happening here” isn’t as catchy.
“Brain tumors” is pretty broad, though. Are these all gliomas? blastocytomas? etc.
Of course it’s well worth investigating; LSLGuy explicitly said that. He* was just noting that the odds of it being random are not zero, and that jumping to conclusions is, as ever, risky.
*I assume that with a handle of “LSLGuy” I can safely say “he” without getting pilloried.
I’d say that there’s definitely something weird here, but that what the weird thing is is most likely just coincidence.
Statistical anomalies do occur. Random doesn’t mean evenly spread, truly random events show “clumpiness”.
Of course it should be investigated but while unlikely it is possible that this is, in fact, a coincidence.
But if they all had colon cancer, or they all had breast cancer, etc. you’d be saying the same thing. And also if they all had some other semi-rare non-cancer disease.
One thing that’s unclear from the article is how many, if any, of these nurses were tested after the pattern was first spotted (or if any of them had tests based on their own suspicions). Probably many people out there have benign brain tumors but don’t know it because they’re asymptomatic.
This changes the odds, and is one of the reasons doctors don’t like overtesting. Lots of people have anomalies that don’t actually pose any health risk and they’d never know about because it only shows up on a scan.
But this is even less remarkable than it seems.
The unmentioned assumption in this is that births are evenly spaced over all 365 days of the year. And that is NOT true. There are clusters of births at specific times during the year.
For example, in the USA culture, there is a mini baby boom 9 months after Valentine’s Day. And a bigger one 9 months after the Holiday season. I expect in Muslim or Asian culture, there would be similar birth clusters, but at different times of the year.
And, often, on a more local basis, nine months after a big snowstorm, or a big power outage. People get bored, and get busy. 
Apparently not:
True, but they might be performed on the floor above or below OB/GYN.
They should also find out about previous employers, or where they went to school, and see if similar clusters existed there.
Two of the cases are reported to be meningiomas. The others are…something different, but also benign.
BTW, even “benign” brain tumors can be pretty nasty, depending on where they’re located and the odds of attaining complete resection.
You’ll get no complaints from me at least.
Although if you’d gotten it backwards I’d have questioned your powers of observation, rather than your gendered pronoun-awareness.
Oh, yes! What are the odds that 5 people who work at the same company and in the same department would have the exact same disease? Virtually zero, I’m sure. It’s not a matter of “if”, it’s a matter of finding it.
Has anything been reported about where the nurses live?
They work at the same hospital. There is a good chance they also live locally.
The connections between these people could extend beyond their work place.
It’s an unusual circumstance, possibly coincidence, possibly not. So the thing to do is investigate, which is happening. Nothing more to the story until more details emerge.
But they don’t have the exact same disease, they have the same broad category of disease.
Granted, but how “broad” of a category is “brain tumor”?
“Over a hundred different kinds” broad.
I don’t know about “far higher”, but I do agree that it’'s nonzero.
If the general population experiences brain tumors at a rate of, say, one in 10,000 (completely made up figure of course) then the odds of having one are 0.0001, and the odds of NOT having one are 0.9999. In a sample of 5, the odds of nobody having one is 0.9999 to the 5th power, or 0.9995. The odds of ALL of them having it are .0001 to the 5th power - basically zero (something like .0000000001, and I know I’ve miscounted the number of zeroes in that figure).
If the hospital has 1000 employees, the odds of nobody having one drop to 90% (0.9999 to the 1000th power).
If you sample any random 5 out of 1000, well, that’s where I could have calculated it a few years back when I took a stats class but I’ve mercifully forgotten most of what I knew.
So… having 5 people developing brain tumors may be possible but it’s pretty unlikely, unless there’s something triggering it.
Reading the article: the tumors are benign (phew… though benign tumors can be life threatening as well). A commenter also mentioned the possibility that some may be due to increased screening after others were diagnosed, and their tumors may never have caused problems. I believe the technical term for this is “incidentaloma” 
I don’t know what the stats are on benign tumors in the gen pop, especially ones found accidentally. The article does not go into details on the type of tumor, whether the nurses had symptoms, what the other “health issues” are, and whether staff OTHER than nurses (aides, cleaning staff, doctors etc.) are. If it’s is something at the hospital, and is something used in patient care, the nurses have more hands-on contact with the patients than other staff would, but you’d think we’d see patterns at other hospitals.
All in all, the article is really vague and seems designed to alarm the population, not inform.