Staging and grading schema have been devised for malignant neoplasms, because the stage and/or grade may determine the treatment and the prognosis. In general, the higher the stage, the larger a neoplasm is and the farther it has likely spread.
The most common systems for staging employs the TNM classification. A "T" score is based upon the size and/or extent of invasion. The "N" score indicates the extent of lymph node involvement. The "M" score indicates whether distant metastases are present. Staging forms have been devised for each organ or site that a malignant neoplasm can occur, and the criteria are listed on the form. The forms are filled out using clinical and pathologic criteria and aid in determination of therapy, estimating the prognosis, and developing statistics useful for determining outcomes.
In the diagram below utilizing a lung carcinoma as an example, the principles of staging are illustrated:
Staging of Malignant Neoplasms
In situ, non-invasive (confined to epithelium)
Small, minimally invasive within primary organ site
Larger, more invasive within the primary organ site
Larger and/or invasive beyond margins of primary organ site
Very large and/or very invasive, spread to adjacent organs
No lymph node involvement
Nearby lymph node involvement
Regional lymph node involvement
More distant lymph node involvement
No distant metastases
Distant metastases present
Grading schema are based upon the microscopic appearance of a malignant neoplasm with H&E staining. (Benign neoplasms are, by definition, always well differentiated.) In general, a higher grade means that there is a lesser degree of differentiation and the worse the biologic behavior of a malignant neoplasm will be. A well-differentiated neoplasm is composed of cells that closely resemble the cell of origin, while poorly differentiated neoplasms have cells that are difficult to recognize as to their cell of origin. Grading schema have been devised for many types of neoplasms, mainly carcinomas. Most grading systems have three or four grades (designated with numbers or roman numerals).
In the diagram below utilizing an adenocarcinoma as an example, the principles of grading are illustrated: