Testicular cancer lumps vs variocele, hydrocele etc

[INJSDN]

I'm 18 and have noticed a "mass" of relatively soft tissue at the top of my left testical. The main lump itself is probably the size of a large pea, but there seems to be a chain of similar tissue leading down from the top (just below the penis base) to the top of the testical itself. I think, though i can't actually remember it being any different, that i have had this for several months, but am worried that it may have become bigger recently and this is the reason i've only just noticed. Having read as much as i can find online i do not know whether it is a sign of cancer or a variocele.

My main question is how hard would a cancerous lump feel? As hard as wood? or plasticine? or like a balloon filled with water?

Many websites say that cancer can be indicated by a "lump", but none mention what this lump would feel similar to if it was cancerous. I have booked an appointment with my GP, but until then i would be greatful if anyone can tell me the difference between what a cancerous and variocele lump would feel like.

Thanks