If you feel a lump in your breast, there is really no way to tell if it is cancerous or benign by the way it feels.
In medical school, we learned about some ways to tell whether it "might" be one or the other and this has lead many in the medical profession to make management recommendations based on the different ways a lump feels. But the truth is that you cannot and should not make an assessment and plan for a breast lump without getting a breast ultrasound, mammogram or both.
Now, it turns out that the vast majority of breast lumps are NOT CANCER. But, in the world of breast health, we have set our needles to "SAFE" rather than "SORRY." So, if you feel a new lump in your breast, it is crucial that you show it to your doctor so that a thorough assessment of the lump can be done.
Do not tell yourself it's probably OK because of how it feels or because it doesn't hurt. Or because your friend had a lump and it was nothing. Get it checked out!