The National Cancer Institute estimates that in 2009, there were 21,550 new diagnoses of ovarian cancer in the United States. Epithelial ovarian cancers begin in the cells that are on the surface of the ovaries. These cancers comprise most of the ovarian cancer diagnoses that are made. There are various kinds of epithelial ovarian cancers that behave differently from one another and carry different prognoses, so it is important to know which kind of cancer has been diagnosed.
Low Malignant Potential Tumors
Some epithelial ovarian tumors are not clearly cancerous underneath a microscope, according to the American Cancer Society. These tumors are called low malignant potential, or LMP tumors. Johns Hopkins Pathology describes these tumors as a kind of borderline cancer that has the potential to grow and invade other tissues and organs. LMP tumors tend to be slow-growing and do not grow into the tissues of the ovary like typical ovarian cancer. Most of the time, these are benign, but they can be malignant and spread.
Malignant Epithelial Ovarian Tumors
Epithelial tumors that are cancerous are called carcinomas. Approximately 85 to 90 percent of ovarian cancer diagnoses are epithelial ovarian carcinomas, according to the American Cancer Society. When examined microscopically, the types of cells in the tumors can vary and are used to classify these tumors into five subtypes. The cell types are: serous (the most common subtype), mucinous, endometrioid, clear cell and transitional cell. Malignant epithelial ovarian carcinomas are also evaluated for how much the cancerous tissue resembles normal tissue; this is called the tumor grade. Grade 1 means the cancerous tissue looks somewhat like normal tissue and carries a better prognosis, whereas Grade 3 cancers do not look like normal tissue and have a worse prognosis.
Primary Peritoneal Carcinoma
A rare cancer that is related to epithelial ovarian cancer is called primary peritoneal carcinoma, or PPC. When surgery is performed, the cancer appears to be epithelial ovarian cancer that has spread throughout the abdominal cavity. When looked at with a microscope, it also appears to be epithelial ovarian cancer. Instead of starting in or on tissues of the ovary, however, PPC begins in the cells of the lining of the pelvis and abdomen, which is called the peritoneum. Treatment for PPC is typically the same as that for advanced ovarian cancer and carries the same prognosis as ovarian cancer that is widespread, according to the American Cancer Society. Other names for this cancer are extra-ovarian primary peritoneal carcinoma and serous surface papillary carcinoma.
