R1.5.4: Differences In Cell Cycle Times

The cell cycle varies in speed between many different human tissues. Bone marrow and gastrointestinal epithelial cells in particular are able to traverse the cell cycle rapidly, often faster than malignant cells. Other cells take much longer to travel through the cell cycle.
In generally, the time for mitosis, synthesis and the G2 phase vary only a little between different cell types (including malignant cells). G1 is the most variable phase, varying from as little as 1-2 hours to tens or hundreds of days.
Therefore, the cell cycle time of a malignant cell is similar to that of normal cells – in that it is not faster than the most rapidly reproducing normal cells, and not slower than the more slowly reproducing cells. The cell cycle for squamous cell carcinomas or adenocarcinomas is typically 30 - 40 hours.