Hello, I am trying to perform a primary culture of tumor tissue using DMEM+1 * ps+10% FBS medium. On the 4th day after inoculating tumor tissue blocks from mice on the culture dish, we observed cells crawling out. After one week of inoculation, we removed the tissue blocks, and the total area of tumor cells did not change significantly in the past month, accounting for only 5% of the area inside the disc. A large amount of vesicular like material appeared in the cells one day ago, but no bacterial or fungal infection was found under a 40x microscope. May I ask what the problem may be? How can I make amends?

Thanks！