Hyperpigmentation ? Bite?

My almost 3 year old mini shih poo/ dachshund mix has developed some sort of (?) on her lower belly area. I am a worry WART and cry often about loosing her lol. So pls steer me in the right direction. I labeled day 1,3,5. The first picture was taken only 5 days ago and that’s when i first noticed a little raised bump light in color it was not there before (almost looked full of puss?) and now it’s this dark red looking mark but not raised. This changed all within the course of 4 days so fast and she’s acting totally normal so I’m not thinking *cancer*.. but also super worried now bc what is this 😭

Hello - I just wamt to start by clearing up a common myth; skin cancer is generally not itchy, or painful.  Therefore an absensce of licking or worrying at a mark does not rule out cancer.  Indeed, the more a mark is worried at, the more I tend to think that its likely to be inflammatory.  However, this is not a consisent enough rule to use to diagnose a mark.

For me, possible diagnoses might include yeast infection, especially given the speed of onset, also trauma, a progressive wound eg burn and possibly also melanoma although I can't remember ever having seen one appear so quickly.   We would strongly reccommend showing these pictures to your vet and given the rate of change, it may be a good idea to ask for triage.

There are some skin lesions that can accompany liver disease, chronic kidney disease or Alabama rot, for example.  They are vot very common but if your vet has any concern about these, they may pick it up on triage and ask to see yourdog sooner.