Just looking around pubmed (online scientific journal database) and stumbled across this recently published article. I thought I'd post this as it is recent and I haven't read about this online.
The experimental group sizes are small which does slightly impact on the validity of this study.
"The following anabolic steroids were used: decadurabulin (50mg once a week intramuscularly) and Winstrol (stanozolol, 18 mg three times per week orally)"
"The aim of the present study was to evaluate DNA damage (micronucleus) and cellular death (pyknosis, karyolysis and karyorrhexis) in exfoliated buccal mucosa cells from anabolic steroid users after 2 months of exposure."
Exfoliated buccal mucosa = naturally, continually lost soft tissue layer on the mouth side of the cheek
"In conclusion, the results of the present study suggest that chromosomal damage and cytotoxicity are induced by anabolic steroids after 2 months of administration in oral mucosa cells [oral mucosa = soft tissues lining the inside of the mouth]. Since DNA damage and cellular death are important steps in events leading to carcinogenesis [development of cancer], this study represents a relevant contribution to the correct evaluation of the potential health risks associated with the consumption of anabolic steroids."
Reference
Martins RA, Gomes GA, Aguiar O, Jr., Medalha CC, Ribeiro DA. Chromosome damage and cytotoxicity in oral mucosa cells after 2 months of exposure to anabolic steroids (decadurabolin and winstrol) in weight lifting. Steroids 2010;75(12):952-5.