For example, if the most prevalent pattern/grade is 2, and the second most prevalent grade is 1, then the Gleason score is 2+1=3. If the neoplasm has only one pattern, the grade of that pattern is doubled to obtain the score. For example  a tumor is all pattern 1, the Gleason score would be 1+1=2. The most differentiated tumor would have the lowest score, Gleason 2 (1+1), while the most differentiated neoplasm (not resembling native prostate tissue) would have a the higest score, Gleason 10 (5+5). Gleason scores range from 2 to 10 , there is no  0 or 1 by definition. Cytological differences between normal prostate to neoplastic glands are evident in changes to the typical two cell layers of the gland. In prostatic adenocarcinoma, the basal (bottom, usually cuboidal type) cell layer is lost, with only the top layer (usally columnar to pseudostratified) remaining. Score descriptions Using this system  the most well-differentiated tumors have a Gleason score/grade of 2, and the least-differentiated tumors a score of 10. Range by definition is from 2-10, with architectural type being from 1-5 and always doubled or added together accordingly as described above. Gleason scores are often grouped together, based on similar behaviour: Grade 2-4 being well-differentiated neoplasm , Grade 5-6 intermediate-grade neoplasm , Grade 7 moderately - poorly differentiated grade neoplasm, Grade 8-10  high-grade neoplasm. Gleason 1 Gleason pattern 1 is the most well differentiated tumor pattern. It is a well defined nodule of single/separate, closely/densely packed, back-to-back gland pattern that does not invade into adjacent healthy prostatic tissue. The glands are round to oval shaped and proportionally large, comparing them to Gleason pattern 3 tumors, and are approximately equal in size and shape to one another. Gleason 2 Gleason 2 are fairly well circumscribed nodules of single, separate glands. However, the glands are looser in arrangement and not as uniform as in pattern 1. Minimal invasion by neoplastic glands into the surrounding healthy prostate tissue may be seen. Similar to Gleason 1, the glands are usually larger than those of Gleason 3 patterns, and are round to oval in shape. Thus the main difference between Gleason 1 and 2 is the density of packing of the glands seen and invasion is possible in Gleason 2,  not in Gleason 1 by definition. Gleason 4 Gleason pattern 4 glands are no longer single/separated glands like those seen in pattern 1-3. They look fused together, difficult to distinguish, with rare lumen formation vs Gleason 1-3 which usually all have open lumens (spaces) within the glands, or they can be cribriform-(resembling the cribriform plate/similar to a sieve . An item with many perforations). Fused glands are chains, nests, or groups of glands that are no longer entirely separated by stroma-(connective tissue that normally separates individual glands in this case). Fused glands contain occasional stroma giving the appearance of "partial" separation of the glands. Due to this partial separation, fused glands sometimes have a scalloped (think looking at a slice of bread with bite taken out of it) appearance at their edges. The majority of treatable/treated cancers are of Gleason scores 5 - 7 and are detected due to biopsy after abnormal digital rectal exam or prostate specific antigen evaluation . A Gleason score of 7 can be 3+4= 7, where the majority is pattern 3, or it can be 4+3=7 in which pattern 4 dominates, resulting in a more advanced stage . The cancer is typically located in the peripheral zone usually the posterior portion, explaining the rationale of performing the digital rectal exam.
For example, if the most prevalent pattern/grade is 2, and the second most prevalent grade is 1, then the Gleason score is 2+1=3. If the neoplasm has only one pattern, the grade of that pattern is doubled to obtain the score. For example , if a tumor is entirely grade 1, the Gleason score would be 1+1=2. The most differentiated tumor would have the lowest score, Gleason 2 (1+1), while the most differentiated neoplasm (not resembling native prostate tissue) would have the higest score, Gleason 10 (5+5). Gleason scores range from 2 to 10 ; by definition there is no score of 0 or 1. Cytological differences between normal prostate and neoplastic glands are evident in changes to the typical two cell layers of the gland. In prostatic adenocarcinoma, the basal (bottom, usually cuboidal type) cell layer is lost, with only the top layer (usally columnar to pseudostratified) remaining. Score descriptions Using this system , the most well-differentiated tumors have a Gleason score/grade of 2, and the least-differentiated tumors a score of 10. Range by definition is from 2-10, with architectural type from 1-5 , and always added together or doubled, as described above. Gleason scores are often grouped together, based on similar behaviour: Grade 2-4 as well-differentiated , Grade 5-6 as intermediately-differentiated , Grade 7 as moderately to poorly differentiated (either 3+4=7, where the majority is pattern 3, or 4+3=7 in which pattern 4 dominates and indicates less differentiation., and Grade 8-10 as " high-grade ." Gleason 1 Gleason pattern 1 is the most well-differentiated tumor pattern. It is a well-defined nodule of single/separate, closely/densely packed, back-to-back gland pattern that does not invade into adjacent healthy prostatic tissue. The glands are round to oval shaped and proportionally large, compared to to Gleason pattern 3 tumors, and are approximately equal in size and shape to one another. Gleason 2 Gleason 2 is fairly well-circumscribed nodules of single, separate glands. However, the glands are looser in arrangement and not as uniform as in pattern 1. Minimal invasion by neoplastic glands into the surrounding healthy prostate tissue may be seen. Similar to Gleason 1, the glands are usually larger than those of Gleason 3 patterns, and are round to oval in shape. Thus the main difference between Gleason 1 and 2 is the density of packing of the glands seen ; invasion is possible in Gleason 2, but by definition not in Gleason 1. Gleason 4 Gleason pattern 4 glands are no longer single/separated glands like those seen in patterns 1-3. They look fused together, difficult to distinguish, with rare lumen formation vs Gleason 1-3 which usually all have open lumens (spaces) within the glands, or can be cribriform-(resembling the cribriform plate/similar to a sieve : an item with many perforations). Fused glands are chains, nests, or groups of glands that are no longer entirely separated by stroma-(connective tissue that normally separates individual glands in this case). Fused glands contain occasional stroma giving the appearance of "partial" separation of the glands. Due to this partial separation, fused glands sometimes have a scalloped (think looking at a slice of bread with bite taken out of it) appearance at their edges. The majority of treatable/treated cancers are of Gleason scores 5-7 and are detected due to biopsy after abnormal digital rectal exam or prostate specific antigen evaluation . The cancer is typically located in the peripheral zone usually the posterior portion, explaining the rationale of performing the digital rectal exam.
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