Is it a Symptom or condition?

My sister has a large raised area on her shin middle way down from the knee.
It appears to be the size of a Half dollar.  It is very dark on top as if it has a scab this area is raised up and has redness surrounding this wound.  I say wound because it looks like an infection. It is very ugly looking.
She does not have insurance, and has gone to a doctor, who said it might be cancer
or cellulitis, he gave her an antibiotic in case it was an infection. It did not improve at all and she went to another doctor who recommend that she see a surgeon to take a biopsy and they would make her an appointment.  That was on December 12th, but now they say they can't get her an appointment for months.  Mean while it is getting bigger and the area has started to run and is very painful.  
What should she do? Do you think it could be a type of cancer?

[medgeek]

Although a biopsy is something that is sometimes carried out by a dermatologist or surgeon, some general practitioner surgeries should be able to do this. She should find somewhere else that can do it without delay. The earlier she gets the biopsy the better, so that if it is cancer she can get treatment before it spreads further.