User:Jdevola/sandbox

In pathology, grading is a measure of the cell appearance in tumors and other neoplasms. Some pathology grading systems apply only to malignant neoplasms (cancer); others apply also to benign neoplasms. The neoplastic grading is a measure of cell anaplasia (lack of differentiation) in the sampled tumor and is based on the resemblance of the tumor to the tissue of origin. Grading in cancer is distinguished from staging, which is a measure of the extent to which the cancer has spread.

Pathology grading systems classify the microscopic cell appearance abnormality and deviations in their rate of growth with the goal of predicting developments at tissue level (see also the 4 major histological changes in dysplasia).

Cancer is a disorder of cell life cycle alteration that leads (non-trivially) to excessive cell proliferation rates, typically longer cell lifespans and poor differentiation. The grade score (numerical: G1 up to G4) increases with the lack of cellular differentiation - it reflects how much the tumor cells differ from the cells of the normal tissue they have originated from (see 'Categories' below). Tumors may be graded on four-tier, three-tier, or two-tier scales, depending on the institution and the tumor type.

The histologic tumor grade score along with the metastatic (whole-body-level cancer-spread) staging are used to evaluate each specific cancer patient, develop their individual treatment strategy and to predict their prognosis. A cancer that is very poorly differentiated is called anaplastic.

Categories
The most commonly used system of grading is as per the guidelines of the American Joint Commission on Cancer. As per their standards, the following are the grading categories.
 * GX               Grade cannot be assessed
 * G1               Well differentiated (Low grade)
 * G2               Moderately differentiated (Intermediate grade)
 * G3               Poorly differentiated (High grade)
 * G4               Undifferentiated (High grade)

Systems
Grading systems are also different for each type of cancer.

The Gleason system, named after Donald Floyd Gleason, used to grade the adenocarcinoma cells in prostate cancer is the most famous. This system uses a grading score ranging from 2 to 10. Lower Gleason scores describe well-differentiated less aggressive tumors. Other systems include the Bloom-Richardson system (breast cancer) and the Fuhrman system (kidney cancer).

Tumor volume estimation
Experimental cancer studies involve the implantation of tumors subcutaneously in mice. Such studies require a simple mechanism by which to evaluate tumor burden. One such method is to approximate the tumor shape by a spheroid. Two researchers blindly measure the tumor length L and width W, in millimeters, with calipers. The depth is not measured and is assumed to equal the width W. The tumor's volume in cubic millimeters is then approximately 0.52W2L.