Primary synchronous bilateral breast cancer: epidemiological approach.

Twenty-eight (1.69%) cases of primary synchronous bilateral breast cancer (PSBC) out of 1,654 new cases were studied. PSBC compared with unilateral cases had a significantly higher (p less than 0.001) first degree family history of breast cancer; high frequency of subareolar location; no predominance of lobular and non-invasive types; no significantly different percentage of pathological stage I presentation. As there is no complete agreement on what constitutes a PSBC, studies should be carried out to formulate a more precise definition of this entity.