The white stuff at the coronal groove of the glans may be foreskin scale. This is due to the fact that when the foreskin is too long, the foreskin cannot be turned upwards, so the sebum secreted by the sebaceous glands of the foreskin will accumulate in the foreskin cavity, and when urine penetrates into the foreskin cavity, it will react chemically with the sebum to form foreskin scale. The actual fact that these parts are not often cleaned, the foreskin scale can accumulate for a long time, and the thicker it gets, the harder it becomes, the more it adheres to the coronal groove of the glans. Since foreskin scale is a chemical carcinogenic substance, on the one hand, it will directly stimulate the head of penis and induce penile cancer; on the other hand, it will lead to frequent inflammation of foreskin and penis head, and long-term inflammation stimulation will cause deterioration of local tissue cells of penis, therefore, foreskin and glans should be cleaned regularly to avoid accumulation of foreskin scale. Then again, if you have a long foreskin, especially a prepuce, you can choose circumcision.