Background WWOX and FHIT are two candidate tumor suppressor genes located in active fragile sites, the damage of which has been associated with the development of breast cancer. The association of the expression of these genes and the development of breast cancer has not been fully explored. We evaluated mRNA and protein expression of WWOX and FHIT in breast tissue with normal histological appearances, atypical ductal hyperplasia, ductal carcinoma in situ, and invasive cancer to see if a progressive decline in expression was present.Methods Reverse transcription-polymerase chain reaction and Western blotting were used to evaluate the specimens for mRNA and protein expression, including 28 specimens with normal tissue, 28 specimens with atypical ductal hyperplasia, 33 specimens with ductal carcinoma in situ, and 51 specimens with invasive ductal carcinoma. Results Compared with in situ and invasive cancer specimens, both normal and atypical hyperplasia specimens had greater rates of detectable mRNA (WWOX rate ratio=2.95, 95% CI 1.24-7.08; FHIT rate ratio=4.58, 95% Cl 1.82-11.81) and Western blotting detectable protein (WWOX rate ratio=4.12, 95% Cl 1.63-10.73; FHIT rate ratio=3.76, 95% Cl 1.44-10.06). For both proteins, differences between normal and atypical hyperplasia specimens and between in situ and invasive carcinoma specimens were explainable by chance (P>0.05 for each analysis). Within each histological category, differences among fractions of specimens showed that FHIT and WWOX mRNA. and protein expression were explainable by chance (P >0.05 for each analysis).Conclusion Expression of FHIT and WWOX decreases along with breast tissue progress from a normal histological appearance to atypical ductal hyperplasia, in situ cancer, and the final invasive cancer.