Breast cancer is occasionally complicated by sclerosing adenosis (SA). Although both lesions usually originate in the terminal duct lobular unit, their pathogenetic relationship has not yet been elucidated. The present study analyzed 63 breast cancer patients with SA (involving a total of 75 breasts) to clarify if coexisting SA increased the frequency of multicentric breast cancer or not. Using the topographical classification proposed in our previous study, breast cancers with SA were classified into the following three types: type A (n = 22), cancer area was completely surrounded by the SA; type B (n = 26), cancer area partially overlapped the SA; and type C (n = 27), cancer area was located separate from the SA. Breast cancers with SA had a significant (P < 0.001) increase in frequency of harboring bilateral and multicentric cancers [17 of 63 (27%) and 15 of 63 (24%), respectively] when compared to breast cancer patients without SA, regardless of topographical type. Breast cancers with SA were less invasive (P < 0.001), of lower histological grade (P = 0.034), and had similar frequency of estrogen receptor-positive (P = 0.21) and HER2-positive (P = 0.74) tumors. In conclusion, contralateral and ipsilateral multicentric breast cancers occurred at a higher frequency in those with SA. Our data suggest that SA is, in addition to lobular neoplasia, a predictor of multicentric breast cancers.