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Inpathology,grading is a measure of the cell appearance intumors and otherneoplasms. Some pathology grading systems apply only tomalignant neoplasms (cancer); others apply also tobenign neoplasms. Theneoplastic grading is a measure of cellanaplasia (reversion ofdifferentiation) in the sampled tumor and is based on the resemblance of the tumor to the tissue of origin.[1] Grading in cancer is distinguished fromstaging, which is a measure of the extent to which the cancer hasspread.
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 indysplasia).
Cancer is a disorder ofcell life cycle alteration that leads (non-trivially) to excessivecell 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.
Thehistologic tumor grade score along with themetastatic (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 calledanaplastic.
Grading systems are also different for many common types of cancer, though following a similar pattern with grades being increasingly malignant over a range of 1 to 4. If no specific system is used, the following general grades are most commonly used, and recommended by the American Joint Commission on Cancer and other bodies:[2]
Of the many cancer-specific schemes, theGleason system,[3] named afterDonald Floyd Gleason, used to grade the adenocarcinoma cells inprostate 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 theBloom-Richardson grading system forbreast cancer and the Fuhrman system forkidney cancer. Invasive-front grading is useful as well in oral squamous cell carcinoma.[4]
Forsoft-tissue sarcoma two histological grading systems are used : the National Cancer Institute (NCI) system and the French Federation of Cancer Centers Sarcoma Group (FNCLCC) system.[5][6]
| Grade 1 | Low grade | Well-differentiated |
| Grade 2 | Intermediate grade | Moderately differentiated |
| Grade 3 | High grade | Poorly differentiated |
| Grade 4 | Anaplastic | Anaplastic |
| Grade 1 | Low grade | Well-differentiated |
| Grade 2 | Intermediate grade | |
| Grade 3 | High grade | Poorly differentiated |
| Grade 1 | Low grade | Well-differentiated |
| Grade 2 | High grade | Poorly differentiated |