Prospective study correlating P120 antigen expression with established prognostic factors in breast cancer.

P120 is a nucleolar proliferation antigen found in rapidly dividing cells and a variety of malignancies. Previous retrospective studies have demonstrated that, when detected in human breast cancer, P120 is associated with a poorer prognosis. To determine whether P120 expression correlates with other prognostic factors in breast cancer, we prospectively analysed pathologic and clinical data from 61 patients. P120 was detected in 40 of the 61 specimens (66%). No significant correlation existed between P120 expression and either tumour size or hormone receptors. A significant correlation was found between P120 expression and histological grade, degree of aneuploidy, S-phase fraction, degree of nodal involvement, and stage of disease. P120 is a biological marker indicative of tumour aggressiveness and may play an important role in determining which patients would most benefit from adjuvant therapy.