My partner has a rather large, about the circumference of a marble, lesion on his scrotum that appears to have roots. It is lighter in pigment than the surrounding tissues. It feels like a knot and is raised, also rough in texture.
It's very difficult to say exactly what something is for certain, with just a brief online description- I'd recommend your partner get to the doctor to have it looked at. The only way to get an accurate diagnosis is for them to have a doctor take more of your partners medical history and do an in person exam.