Ovarian cancer is a type of malignant tumor that originates from cells in the ovary. Very often it is diagnosed only when it has spread to the pelvis and abdominal cavity. At this advanced stage, the disease is much more difficult to treat and usually has a poor prognosis. Ovarian carcinoma is the sixth most common malignant tumor among women in Europe. In Bulgaria, about 421 women die annually with this diagnosis. The type of cells from which the tumor originates determine the type of ovarian cancer. They can be: Epithelial tumors. They begin their development from the thin layer of tissue covering the outside of the ovaries. It occurs in about 90% of ovarian cancers. Stromal tumors. This type of tumor begins its development from the hormone-producing stromal cells of the ovary. These tumors are usually diagnosed at an earlier stage and account for about 7% of all ovarian tumors. Germinal tumors. They develop from the germ cells of the ovary that produce the eggs. They usually affect younger women. As with most malignant tumors, carcinogenesis in these cases involves a number of genetic changes. Ovarian cell dedifferentiation can occur both due to the multistep mutational process and due to genetic instability leading to an accelerated process of metastasis. Ovulation plays an important role in the pathogenesis of the disease – repeated processes of DNA damage, inflammatory changes, restoration of the surface epithelium and others. This hypothesis also coincides with the most important clinical risk factors (absence of childbirth) and protective factors (taking oral contraceptives, breastfeeding, prophylactic oophorectomy). Another factor increasing the risk of the disease is obesity. Early menarche and late menopause increase the risk of ovarian carcinoma. A small percentage of women with epithelial ovarian carcinoma have a family history. Mutations in the BRCA1-BRCA2 genes are found in them, which significantly increases the risk of developing ovarian cancer or breast cancer. It has been proven that these genes are involved in the processes of DNA repair – when exposed to a corresponding carcinogen, cells with a mutation are more difficult to restore the damaged DNA molecule. Very often, the disease proceeds atypically with heaviness in the abdomen, irregular menstrual cycle, tension in the small pelvis, nausea, dyspeptic complaints, increased abdominal girth, frequent urination or constipation. These symptoms are usually late and very non-specific. Very often the first symptoms are intestinal obstruction due to compression by intra-abdominal tumor masses. Difficulty breathing may also occur in the presence of a pleural effusion. When tumor masses in the small pelvis are established, a study of the tumor marker CA 125 is resorted to. However, it is not always specific, as it is influenced by various factors and especially by processes in the small pelvis. Such processes can be inflammatory changes in the peritoneum of other origins (endometriosis,adenomyosis, benign cysts, menstrual cycle). Whether the result is a false positive can be understood if the marker is examined in dynamics. A progressive increase in CA 125 indicates the presence of epithelial ovarian carcinoma. About 15% of ovarian carcinomas are diagnosed at stage four. References: 1. Epithelial Ovarian Cancer and the Immune System: Biology, Interactions, Challenges and Potential Advances for Immunotherapy Published online 2020 Sep 14. 2. https://www.cancerresearchuk.org/about-cancer/ovarian-cancer/types 3 Medical Oncology edited by Prof. K.V. Timcheva, 2018.