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What is The most important prognostic factor in carcinoma breast is and explain in detail?
The Nottingham prognostic index (NPI) is used to determine prognosis following surgery for breast cancer. 
Its value is calculated using three pathological criteria: the size of the lesion; the number of involved lymph nodes; and the grade of a tumour.
Size of the lesion is least important.
The extent of axillary lymph node involvement by breast cancer—is the most established and reliable prognostic factor for subsequent metastatic disease and survival