Serous cystadenoma of the ovary

What is a serous cystadenoma?

A serous cystadenoma is a very common non-cancerous type of ovarian tumour. It develops from the cells on the surface of the ovary. While these tumours are non-cancerous, they can grow to be very large in size and as a result can cause significant symptoms for many patients.

The  ovary and fallopian tube

The ovaries are part of the female reproductive tract. They are small organs that are attached to the uterus by the fallopian tubes. The outer surface of the ovaries are lined by a thin layer of specialized tissue called the epithelium that forms a barrier around the outside of the ovary. The organs inside the abdomen are lined by a thin layer of tissue called the peritoneum that is made up of similar cells. The ovaries also contain large cells called eggs. The tissue below the epithelium is called the stroma.

Gynecological tract

How do pathologists make this diagnosis?

For most women, the diagnosis of serous cystadenoma is only made when the entire tumour has been surgically removed and sent to a pathologist for examination. The fallopian tube and uterus may be removed at the same time.

Your surgeon may request an intraoperative or frozen section consultation from your pathologist. The diagnosis made by your pathologist during the intraoperative consultation can change the type of surgery performed or the treatment offered after the surgery is completed.​

Most tumours are similar in look and feel to a balloon filled with fluid. The inside of the tumour may be one large space or many small spaces filled with fluid. Pathologists call these spaces cysts.

When the tumour is examined under the microscope, the tissue on the inside of the cysts is made up of an abnormal type of epithelium made up of serous cells. These cells produce a fluid that fills the inside of the tumour. Some tumours will have thicker walls or solid areas in the centre of the tumour. These tumours contain more cells and less fluid and are called serous adenofibromas. However, they are still non-cancerous.

Surface of the tumour

Most serous cystadenomas have a smooth outer surface. Any solid areas on the surface will be examined closely under the microscope to make sure they do not contain any abnormal cells.

Atypical cells in a serous cystadenoma

The cells in a serous cystadenoma usually look very similar to the normal cells that line the outside of the ovary. However, some tumours may have cells that look different. Atypical cells are tumour cells that are larger or darker than normal cells. Although they are abnormal-looking, atypical cells are not cancer cells.

Papillary growth in a serous cystadenoma

The inside of most serous cystadenomas are lined by a flat single layer of cells. When examined under the microscope, however, some tumours have small growths that look like little fingers. Pathologists describe this pattern of growth as papillary. Serous cystadenomas with papillary growths are still non-cancerous.

by Jason Wasserman MD PhD FRCPC (updated September 1, 2021)
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