Most important prognostic factor for carcinoma breast is
Skin involvement
Tumor size
Chest wall involvement
Lymph node involvement
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.