Surface epithelial-stromal tumors are a class of ovarian neoplasms that may be benign or malignant. Neoplasms in this group are thought to be derived from the ovarian surface epithelium (modified peritoneum) or from ectopic endometrial or Fallopian tube (tubal) tissue. Tumors of this type are also called ovarian adenocarcinoma. This group of tumors accounts for 90% to 95% of all cases of ovarian cancer; however is mainly only found in postmenopausal women with the exception of the United States where 7% of cases occur in women under the age of 40. Serum CA-125 is often elevated but is only 50% accurate so it is not a useful tumor marker to assess the progress of treatment. 75% of women with epithelial ovarian cancer are found within the advanced-stages; however younger patients are more likely to have better prognoses than older patients. Classification Epithelial-stromal tumors are classified on the basis of the epithelial cell type, the relative amounts of epithelium and stroma, the presence of papillary processes, and the location of the epithelial elements. Microscopic pathological features determine whether a surface epithelial-stromal tumor is benign, a borderline tumor, or malignant (evidence of malignancy and stromal invasion). Borderline tumors are of uncertain malignant potential. This group consists of serous, mucinous, endometrioid, clear cell, and brenner (transitional cell) tumors, though there are a few mixed, undifferentiated and unclassified types. Serous tumors These tumors vary in size from small and nearly imperceptible to large, filling the abdominal cavity. Benign, borderline, and malignant types of serous tumors account for about 30% of all ovarian tumors. 75% are benign or of borderline malignancy, and 25% are malignant The malignant form of this tumor, serous cystadenocarcinoma, accounts for approximately 40% of all carcinomas of the ovary and are the most common malignant ovarian tumors. Benign and borderline tumors are most common between the ages of 20 and 50 years. Malignant serous tumors occur later in life on average, although somewhat earlier in familial cases. 20% of benign, 30% of borderline, and 66% of malignant tumors are bilateral (affect both ovaries). Components can include: cystic areas cystic and fibrous areas predominantly fibrous areas The chance of malignancy of the tumor increases with the amount of solid areas present, including both papillary structures and any necrotic tissue present. Pathology lined by tall, columnar, ciliated epithelial cells filled with clear serous fluid the term serous which originated as a description of