We don't know. I posted a pic in the beginning of the thread. Kind of like a second chin on a human, but it became way too large for her. Still she ate and pooped normally, even pooped since last night. Vet did a biopsy when we first brought her in, but didn't find anything. Medicine did not help either. I am checking with her if she wants to do an autopsy. Might help others, who knows.
I am so sorry to hear that you lost little Spike, I know it is a horrible empty feeling.
It was likely some type of abscess that traveled through her body, or a tumor. My sincere
condolences to you.