In the cells of some organisms, mitosis occurs without cytokinesis. this will result in cells with multiple nuclei.

Explanation:
Firstly, what is mitosis?
Mitosis is a type of cell division that occurs in eukaryotic cells to produce two identical daughter cells, each with the same number and kind of chromosomes as the parent cell.

What is cytokinesis?
Cytokinesis is the final stage of the cell division process, following the completion of mitosis, and is the physical separation of the two daughter cells. In cytokinesis, the cytoplasm of the parent cell is divided between the two daughter cells.

So, clearly without cytokinesis, genetic material and chromosome duplication will happen, forming multiple nuclei but as final cell division doesn’t happen, it will lead to cells with multiple nuclei or a multinucleated cell.

Examples of mitosis without cytokinesis is seen in
1. Bone cells (osteoclasts)
2. Fruit flies during early development