Is this true?..35 percent of people who have high platelet counts also have cancer... sometimes a high platelet count is the first sign of cancer.

Thrombocytosis: Yes a high platlet count can sometime be a sgn of cancer.

Yes and No: Cancer is a differential diagnosis for folks with high platelet counts. But what count of platlets is "high" is a matter of some uncertainty. Not all platlet counts above the upper limit(350k) have the same significance. So all i can say is that one should be alert to notice a high count and keep an eye because in some cases cancer can be occult and high platelet count can be a paraneoplastic synd.

Misleading: People with known cancer are more likely to have blood counts in the first place. And how high is "high"? One of the fuzziest reference ranges in any lab is the upper limit on platelet counts. Most people fall at 300, 000 or under, but hematologists are unlikely to take notice until we're above 500, 000. If your routine cancer surveillance is non-revealing, you owe it to yourself to stop worrying.

No: Your platelet count may go up with exercise and even infection. There is no link to cancer but you may have a clotting problem if the count gets really high.