The cancer can occur in the scrotum
.It can present like swelling over the scrotal skin which ulcerates later.
As per your query,it does not look like cancer.
As the blood vessels are like channels,once pressure is applied,it becomes lighter at the site of pressure.
Later it fills up once the pressure is removed
Colour doppler of the scrotum will confirm any disease if at all present.
Nothing to worry
Wish you good health