Cancers of the lip strike hundreds of thousands of people every year. Cancers of the mouth and lips make up over 50 percent of all cancers in India, Bangladesh, and Sri Lanka, and they are the leading form of cancer among men in France. All over the world more and more people are developing cancers of the lips, at younger and younger ages. Lip cancer is less common among people of African heritage, but it can strike just about anyone at any age anywhere on earth.  Here are 10 ways to tell if you need to see the doctor.
1. Cancerous and precancerous lesions of the lips don't come and go.
Chapped lips can get better and worse. Cancer and precancer just get worse. Remember the RULE. If it's red or ulcerated (failing to heal, whether red or purple) or it's a lump or it extends for more than three weeks, it could be cancer. 
2. Red is dread, but white is no reason for sudden fright.
Velvety red patches on your lip, whether they are dry or suppurative (oozing), are cancerous 85 percent of the time. White patches are likely to be pre-cancerous. A patch with red or purple of white spots is also likely to be precancerous. You need to get a doctor to diagnose dark red patches right away. You have a month or more, probably, if the patch is white. 
3. Lip cancers don't always appear on the surface of the lip.
Sometimes a relatively advanced lip cancer will be barely detectable on the surface of the lip. It may cause a lump underneath the lip, or even be visible for the first time as a swollen lymph node .
4. If you have had HPV infection, or your partner has had HPV infection, and you have engaged in oral sex, you are at increased risk for cancer of the lip.
The same virus, human papillomavirus, that causes genital warts can also cause cancers of the lip. . Even children who have never had sex, however, can get cancers of the lip and mouth caused by HPV to which they were exposed during birth . HPV infection most often causes cancer when something has compromised the immune system . This could be HIV infection, chemotherapy, or extreme stress.
5. Lip cancers are most likely to form at the junction of the lip and the lining of the mouth.
The most frequent site of lip cancers is at the mucocutaneous junction, where the dryer, tougher skin of the lip meets the moister, soften mucosal lining of the mouth. If you frequently bite your lip, you can tell the difference between a cancer and a bit by how it scabs. You will have a crustier scab from a cancer than from a bite.
6. Lip cancers are usually solitary. They don't form in pairs or bunches.
Only about 10 to 15 percent of people who develop lip cancers will have multiple cancer sites. On the other hand, untreated lip cancer often spreads to the lymph glands of the neck.
7. Certain medications increase your risk of lip cancers.
The blood pressure medication amlodipine (Norvasc) increases your likelihood of mouth and lip cancers  Medications that increase your sensitivity to sunlight like ACE inhibitors for high blood pressure (lisinopril, captopril, and similar drugs) and psoralens for psoriasis also increase the risk of sun damage to your lips, as can overdosing on vitamin D (taking more than 10,000 IU per day on a regular basis) or St. John's wort.
8. Any patch on your lip that increases in size for 10 to 14 days or more is potentially cancerous.
If you try chapped lips remedies for a couple of weeks and the area of dry or irritated skin is increasing, you need to see your to rule out cancer. If you have a sore place from some kind of friction on your lip (lip piercing, for example) and it doesn't clear up in 10 to 14 days, you need to see your doctor to rule out lip cancer. .
9. Dry patches on your lip that become painful are a cause for immediate concern.
Basal cell carcinoma may hurt night and day. A pearl-like lesion on your lip, even if it is white or gray, may be cancerous.
10. Lifestyle choices indicate the likelihood of lip cancer.
There are lifestyle choices that make a difference in your risk of lip cancer, but that aren't a cause for alarm unless you have taken them to extremes. Smoking increases your risk of lip cancers, but it's heavy smokers who need to see a doctor at the first signs of lip cancer. Marijuana use increases your risk of lip cancer, but it's people who smoke more than five times a day who have especially high risk of lip cancer. Multiple sex partners increase your likelihood of acquiring a virus that causes lip cancer, but it is people who have had oral sex with 20 or more partners who are most likely to get cancer. Be frank about your lifestyle with your doctor, but don't panic about these relatively minor considerations. They are mostly helpful to your doctor to know what to rule out as the problem. No lifestyle factor, not even smoking or a lifetime of outdoor activity in the sun, increases your risk of lip cancer more than about 50 percent.