"Direct link found between smoking and lung cancer," ran the headline in the most influential real estate in all American journalism: page one, above the fold, in the New York Times.

But the story wasn't Sir Richard Doll's 1952 study showing that smokers are vastly more likely than nonsmokers to develop lung cancer. And it wasn't the US Surgeon General's 1964 report declaring that cigarettes cause lung cancer. The subject was a 1996 report in Science, detailing how one of the more than 40 carcinogens in cigarette smoke causes mutations in p53, a gene linked to lung cancer (and other malignancies).

There's no question that the study was a tidy little piece of molecular biology. But it's rather remarkable how some reporters dressed up the finding to give it the air of a revelation. The New York Times report was propelled, among other things, by the words of anti-smoking law professor John Banzhaf, who was quoted saying, "This is very important in imposing liability on the cigarette industry and in protecting nonsmokers from secondhand smoke."

Dealing with a small but interesting finding is always a delicate balancing act. The trick is to make it newsworthy without overblowing its significance. Many in the US media overreached on this one by suggesting that, until now, there has been no 'smoking gun' linking tobacco smoke to lung cancer.

For starters, many stories downplayed or ignored mounds of previous studies, dating back to the 1950s, linking the carcinogen in question, benzo(a)pyrene, to all sorts of cancers. Many also ignored previous molecular biology showing that benzo(a)pyrene has been shown to mutate p53 ? and that p53 mutations have been found in many lung cancer cells.

What was new was this nuance: in cell culture, benzo(a)pyrene causes the same mutations in p53 as are found in about 60% of all lung cancers. But ignoring the previous molecular studies, the Wall Street Journal reported that "Until now, the conviction that smoking causes lung cancer has rested largely on epidemiological evidence . . . and toxicology." The New York Times noted that "While many scientists have long been convinced by statistical studies and animal experiments that tobacco causes cancer, a statistical association was not in itself absolute proof." But that report, and others, didn't mention that, even with this much molecular detail, the finding is still fundamentally a correlation, not "absolute proof" that would once and for all deny the tobacco industry its semantic argument about causality and lung cancer.

Although reporters may be given some latitude for skipping over the scientific history of this field (which was outlined in the Science article itself), they should have been more aware of the legal implications of the finding. Numerous news outlets relied on the opinion of John Banzhaf that the discovery would make a huge difference in court cases against tobacco companies, as tobacco companies are now deprived of their argument that there's no proof that smoking causes cancer. "It's confirmation of what we have known before," Banzhaf told the Associated Press, "but it makes it easier for us now to demonstrate it in court."

In fact, tobacco companies don't rely on that argument in court anymore. They usually argue instead that people know smoking is risky (it says so on every pack of tobacco) but they freely choose to keep at it anyway. That's why one of the nation's leading anti-tobacco experts, Stanton Glantz at the University of California at San Francisco, told the Los Angeles Times, "I think it's a nice piece of science that helps get at a mechanism but I don't see it as having a major public health or legal or political impact." The head of the National Cancer Institute's tobacco control program, Donald Shopland, echoed that sentiment in other news reports.

The R.J. Reynolds Tobacco Company was so delighted to read Glantz's words that it sent out a press release quoting him. And Glantz says, for once, the tobacco company got it right. Even so, tobacco stock prices dropped sharply on the day the news reports appeared (though there was other, unrelated, bad news on the legal front that day for the tobacco industry).

Reporters who cover tobacco regularly were more careful with the story. Doug Levy at USA Today noted in his short report that researchers had previously identified p53 mutations in smoking-induced lung cancers. The San Francisco Examiner, on the other hand, made an embarrassing stab at explaining the story in an editorial: "Our bodies are built from millions of tiny cells," it begins. "Each has a nucleus. Inside, bathed in DNA, are microscopic chromosomes encrusted with itsy-bitsy doodads called genes." The editorial ends with a simple word of advice about smoking that the writer should have taken to heart several paragraphs earlier: "Quit."