There is a lump (about 1.18 inches to 1.57 inches in diameter) on my right buttock for a very long period (about 15 to 18 years). Perhaps it is not regular shaped (not fully round or oval). It might have increased a little within the last five years, and now it might be 1.77 inches to 1.96 inches in diameter. It pains a little only when it gets pressed. Otherwise, it does not create any problem. I checked with a dermatologist eight years back, and he said that it was a sebaceous cyst. But he said it just by looking at the lump. He did not examine it physically. The lump is firm upon palpation. When I sit for some time, it gets compressed and decreases in size, and again reverts to its original size. Now I fear it to be anything serious like cancer. Please help.