Most important prognostic factor for carcinoma breast is
Spread to axillary nodes is the most important prognostic indicator. 
Other prognostic factors are
Age: Younger the age worse the prognosis. 
Sex: Carcinoma male breast has got worse prognosis compared to the female breast. Because of early spread in carcinoma male breast.
Stage I and II have got a better prognosis. 
Atrophic scirrhous has got the best prognosis.
Medullary carcinoma has got better prognosis than scirrhous carcinoma because of lymphocytic infiltration.
Invasive carcinoma has got a worse prognosis. 
Inflammatory carcinoma breast has the worst prognosis.
Skin involvement
Tumor size
Chest wall involvement
Lymph node involvement