This week in pathology I continued to learn more about characterizing slide-mounted tissue samples; specifically, I focused on tumor grading. Relatively straight-forward, yet very subjective, tumor grading is a process that breast pathologists enjoy on a daily (if not hourly) basis. Grading a tumor is based upon both cytology (how the cells in the specimen generally appear) and architecture (organization of both the cellular and non-cellular components of a tissue). For breast tissue, the important characteristics are: how well-defined cellular tubule structures are, how atypical the cell nuclei are (in absolute size, size relative to the rest of the cell, and general appearance), and the frequency of cell division. Each of these are graded on a scale of 1-3.
While the grade of a tumor is primarily useful to pathologists, tumor staging is used universally by oncology clinicians, cancer researchers, and cancer patients. The "stage" of a cancer refers to three factors: tumor status (essentially the size of the tumor, 1-4), the nodal status (degree of regional lymph node involvement, 0-3), and systemic metastases (0 or 1). Pathologists are responsible for determining both the tumor and nodal status.