32 year old female, rash on one nipple, worried it might be cancer?

Biopsy: Often a skin biopsy is indicated to tell if the condition is benign or if it is cancerous. See a doctor for an evaluation and examination to see what may be indicated for your condition.

Check with your doc: Often it could be as simple as contact rash, fungal rash or early infection. Common thing tend to occur commonly and you should check with your doc for reassurance.