Cancer and HIV. Not the most charming bedfellows, but researchers have long noted that HIVers have higher rates of certain cancers. Some, such as Kaposi’s sarcoma, non-Hodgkin’s lymphoma and cervical cancer, herald an AIDS diagnosis. Now it’s becoming clear that some other cancers are more prevalent in HIVers, too. Lung cancer is three times likelier to hit HIVers than negative folk and five times more after the onset of AIDS, according to Sam Mbulaiteye, MD, of the National Cancer Institute. (Estimates put lung cancer in non-HIVers at about one in 1,000 per year for men and a bit lower for women.) Hodgkin’s lymphoma occurs 10 times more among people with HIV.

In HIVers, these—like melanoma and testicular, anal and genital cancer—progress faster and appear at a more advanced stage and younger age. Symptom confusion may hurt if, say, a doc pegs an HIVer’s cough as pneumonia, not lung cancer.

Docs had long assumed that HIVers’ immune systems could not guard against emerging tumor cells. But Mbulaiteye says it may not be immune weakness or HIV that’s increasing the cancer risk, which, according to his team’s data, doesn’t seem to correlate with CD4 counts—even though counts under 200 are one sign of AIDS. Instead, he cites factors like smoking and HIV’s association with other cancer-causing viruses, such as Epstein Barr virus (linked with lymphoma) and human papillomavirus. It could also be an effect of HAART. But for now, Mbulaiteye says, we just don’t know.