<prompt> The most important prognostic factor in carcinoma breast isSize of tumourSkin involvementAxillary gland involvementInvolvement of muscles  <response>: 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 canceris the most established and reliable prognostic factor for subsequent metastatic disease and survival 