Hello... My Sister Is 65 Years Old And Has Been

Hello... my sister is 65 years old and has been suffering from severe abdominal / back / skin pain for nearly two months now. She's had a host of tests done which revealed nothing. She did have a petscan which "lit up" as the dr. told her but he also said that not only cancer "lights up" but her sarcoidosis could do the same. Anyway..... she was diagnosed about a moth ago w/ cellulitis of her back and put on antibiotic for 7 days. She continues to have the skin pain w/ numbness (sounds crazy huh ?) and wondered if maybe she should have had longer anitbiotic care. Thanks...