I'm not entirely sure what I'm asking. . . I guess, whether it sounds like what I'm describing is most likely related to Harry (my cat)'s cancer. Harry had osteosarcoma, and just recently an aggressive spindle cell tumour - both of which were removed with clean margins through amputation (first a leg, then a toe). 

Harry has recently had lumps popping up all over. They are in his skin, don't cause him pain, are sort of move-able, and range from very tiny to just larger than a pea in size. It seems like I'm finding a new one every couple of days. There are a few on the back of his head. A few on his lower back. One big one on his shoulder blade (which has been there the longest and was aspirated by the vet who said it looked unsuspicious at the time). A couple on the underside of his neck...I haven't noticed any on his limbs, sides, or stomach (although this isn't really an area that he lets me pet). 

I've also just noticed a bigger lump, that feels more like it's attached to muscle or something undereath, behind his jaw. This also doesn't seem to cause him discomfort when touched. 

Can the types of cancer Harry has had spread like that? 

Could another type of cancer be eating away at him? 

I feel like my boy is on his last legs, and that our next vet visit will be to have him put to sleep. I don't want to put him through anymore tests because I really don't think he has long left...he is mostly sleeping, and is reluctant to move around right now...he eats pretty well still, but I am either bringing him his food or bringing him to his food. He's only pooping every few days. Sometimes I think he's in pain. Other times I think he's just being lazy and is irritated by the construction zone we're currently living in. He's still grooming and interested in stuff going on around him....I'm starting to suspect that his elbow is being eaten away in the same way his toe just was (it happened in less than a month), because in the last few days he has been particularly reluctant to bend it and has had a minor reaction when I press against the outside of the joint...a warning nip, or a flinch 🙁 ............anyway. He's a trooper, but I think we're nearing the end. I just wonder about the lumps...I'm no cancer expert and I just want to understand what's happening to him better.