by Jason Wasserman MD PhD FRCPC
March 7, 2023
A cellular leiomyoma is a non-cancerous tumour that starts in the muscular wall of the uterus. The tumour is made up of specialized smooth muscle cells that are normally found in a part of the uterus called the myometrium. The tumour is called ‘cellular’ because it contains more cells than the surrounding normal myometrium.
Small cellular leiomyomas typically do not cause any symptoms. Larger tumours can cause symptoms such as abdominal pain, pressure, and vaginal bleeding.
In the uterus, there is no difference between a cellular leiomyoma and a fibroid. Both terms are used to describe the same type of non-cancerous tumour.
Cellular leiomyomas are often diagnosed after all or a part of the uterus has been removed and tissue has been examined under the microscope by a pathologist. For many patients, the uterus is removed for other reasons and the tumour is found incidentally.
When examined under the microscope, a cellular leiomyoma is made up of long thin cells called spindle cells. The number of cells in the tumour is typically much greater than the number of cells in the surrounding normal myometrium. The spindle cells in the tumour are often described as growing in fascicles which are long interconnecting chains of cells. Thick-walled blood vessels and open spaces called cysts are commonly seen. Rare mitotic figures (tumour cells dividing to create new tumour cells) may also be seen.
Degenerative change is a term pathologists use to describe the breakdown of tissue over time. It is very common to see degenerative changes in a cellular leiomyoma, especially larger ones that have been growing for a long time.
Some cellular leiomyomas grow so large that blood cannot get to all of the cells in the tumour. The cells that do not receive blood undergo a type of cell death called necrosis and the area of the tumour that dies is described as an infarct. Infarct-like necrosis is very common in tumours that have been treated with hormone therapy or embolization.