Grading (tumors)

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 tumors arising from the hyperplasia of normal tissue. Grading in cancer is distinguished from staging (Cancer_staging) that is instead a measure of the extent the cancer has spread.

Pathology grading systems classify the microscopic cell appearance abnormality, deviations in their rate of growth, degree of invasiveness and dissemination 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.^{[citation needed]} 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^[1], 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).

Examples of grading schemes

Four-tier grading scheme

Grade 1	Low grade	Well-differentiated
Grade 2	Intermediate grade	Moderately-differentiated
Grade 3	High grade	Poorly-differentiated
Grade 4	Anaplastic	Anaplastic

Three-tier grading scheme

Grade 1	Low grade	Well-differentiated
Grade 2	Intermediate grade
Grade 3	High grade	Poorly-differentiated

Two-tier grading scheme

Grade 1	Low grade	Well-differentiated
Grade 2	High grade	Poorly-differentiated

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.^[2]

See also

• TNM#Other parameters
• Tumor kinds that have their own grading system:
  • Teratoma
• Gleason score

References

1. ^ Gleason, Donald F; Mellinger George T, (Feb. 2002). "Prediction of prognosis for prostatic adenocarcinoma by combined histological grading and clinical staging. 1974" (in eng). J. Urol. (United States) 167 (2 Pt 2): 953–8; discussion 959. doi:10.1016/S0022-5347(02)80309-3. ISSN 0022-5347. PMID 11905924. 
2. ^ W. Su & Q. Wang: Inhibition of Human Prostate Cancer Growth and Prevention of Metastasis Development by Antiangiogenic Activities of Pigment Epithelium-Derived Factor. The Internet Journal of Oncology, 2007 Volume 4 Number 1

External links

• National Cancer Institute
• CancerWeb
• unice.fr