Serous tubal intraepithelial carcinoma (STIC)

What is serous tubal intraepithelial carcinoma (STIC)?

Serous tubal intraepithelial carcinoma (STIC) is a non-invasive type of fallopian tube cancer. It develops from the cells in the epithelium of the fallopian tube.  The tumour is described as non-invasive because the cancer cells are only seen in the epithelium. STIC is a pre-cancerous disease that can, over time, turn into an invasive type of cancer called high-grade serous carcinoma.

The fallopian tube

The fallopian tubes are thin hollow structures that connect the ovaries to the uterus.  During ovulation, the egg is released from the ovary and travels to the uterus through the fallopian tube.

The inside of the fallopian tube is lined by a single layer of specialized epithelial cells. These cells have small hair-like projections on one end of the cell called cilia. The cilia help push the egg down the fallopian tube after ovulation. The epithelial cells form a barrier on the inside of the fallopian tube called the epithelium. Below the epithelium is a layer of muscle. The outer surface of the fallopian tube is made up of a thin layer of loose connective tissue called serosa.

Gynecological tract

Genetic syndromes associated with serous tubal intraepithelial carcinoma

Patients who have had breast cancer and/or genetic testing showing a mutation in the gene BRCA are at risk for STIC and may have their fallopian tubes and ovaries removed prophylactically, meaning that these organs are removed prior to the diagnosis of STIC or carcinoma in order to reduce the risk of disease.

How do pathologists make this diagnosis?

The diagnosis can only be made after the fallopian tube is examined under the microscope by a pathologist. This diagnosis can be made alone or in women who have also been diagnosed with high-grade serous carcinoma of the ovary. In some cases, the diagnosis is made after the fallopian tube is removed for other reasons such as tubal ligation for family planning.

Your pathologist may perform a test called immunohistochemistry on your tissue sample to confirm the diagnosis. The cells often show abnormal expression of a protein called p53. That means that p53 will be either strongly positive or completely negative (null).

Ki-67 is a protein that increases when cells are dividing.  In STIC, Ki-67 is usually increased and your pathologist may describe the percentage of cells that are positive for the protein. This is called the proliferative index and in STIC it is typically greater than 40%.

by Emily Goebel, MD FRCPC (updated July 28, 2021)
A+ A A-