| Fibrosis (modified from reference 19) | |
| 0 | No reticulin fibers demonstrable or only occasional fine individual fibers |
| 1 | Occasional fine individual fibers plus foci of fine fiber network |
| 2 | Fine fiber network throughout most of the section; no coarse fibers demonstrated |
| 3 | Diffuse, fiber network with scattered thick, coarse fibers, but no fine collagen (negative trichrome stain) |
| 4a | Diffuse, often coarse, fiber network with focal (< 10% marrow area) areas of collagenization (positive trichrome stain). |
| 4b | Diffuse coarse fiber network with < 50% marrow area collagenized (positive trichrome stain) |
| 4c | Diffuse coarse fiber network with > 50% marrow area collagenized (positive trichrome stain) |
| Osteosclerosis (modified from reference 21) | |
| 0 | Normal bone |
| 1 | New bone formation |
| 1a | 1 or 2 foci of appositional new bone formation |
| 1b | 3 or more foci of appositional new bone formation |
| 1c | Severely abnormal trabeculae composed of woven bone |
| 2 | Thickened lamella bone with disordered matrix |
| Cellularity | Percentage of bone marrow space occupied by hematopoietic cells |
| Fibrosis (modified from reference 19) | |
| 0 | No reticulin fibers demonstrable or only occasional fine individual fibers |
| 1 | Occasional fine individual fibers plus foci of fine fiber network |
| 2 | Fine fiber network throughout most of the section; no coarse fibers demonstrated |
| 3 | Diffuse, fiber network with scattered thick, coarse fibers, but no fine collagen (negative trichrome stain) |
| 4a | Diffuse, often coarse, fiber network with focal (< 10% marrow area) areas of collagenization (positive trichrome stain). |
| 4b | Diffuse coarse fiber network with < 50% marrow area collagenized (positive trichrome stain) |
| 4c | Diffuse coarse fiber network with > 50% marrow area collagenized (positive trichrome stain) |
| Osteosclerosis (modified from reference 21) | |
| 0 | Normal bone |
| 1 | New bone formation |
| 1a | 1 or 2 foci of appositional new bone formation |
| 1b | 3 or more foci of appositional new bone formation |
| 1c | Severely abnormal trabeculae composed of woven bone |
| 2 | Thickened lamella bone with disordered matrix |
| Cellularity | Percentage of bone marrow space occupied by hematopoietic cells |