A serous tumour is a neoplasm that typically has papillary to solid formations of tumor cells with crowded nuclei. They typically arise on the modified Müllerian-derived serous membranes that surround the ovaries in females. Such ovarian tumors are part of the surface epithelial-stromal tumour group of ovarian tumors. They are common neoplasms with a strong tendency to occur bilaterally, and they account for approximately a quarter of all ovarian tumors.
Rarely, serous tumors arise from other parts of the peritoneum, including serous primary peritoneal carcinomas. Even more rarely they arise in other body locations, such as the lungs. Despite the name, uterine serous carcinoma arises from the endometrium and not the serous membrane.
Ovarian serous tumours
Low grade
thumb|270px|Histopathology of invasive low-grade serous carcinoma of ovary with typical features. H&E stain. The left image shows lower magnification, including inverted macropapillae which are with broad fibrovascular cores surrounded by clear (white) clefts. Invasion (characterized by small irregular nests to single cells) should be over 5 mm in size to distinguish it from a borderline serous tumor. Calcifications often form psammoma bodies. Right picture shows higher magnification, including hobnailing which is individual cells protruding into the lumen of glands. Cells may have up to moderate atypia: They may have conspicuous nucleoli, and up to 3x variation in nuclear sizes compared to each other. More atypical features indicate a high-grade serous carcinoma.
The "low grade" classification of serous tumors includes benign and borderline tumors, as well as low grade malignant tumors. Benign serous tumors are distinguished from borderline tumors by the absence of cellular stratification. Stromal invasion distinguishes borderline tumors from low grade malignant tumors.]]
High grade serous tumors often involve both ovaries. The tumors are solid and cystic with haemorrhage and necrosis. They are morphologically heterogenous. and 40% of ovarian cancers are serous tumors. Family history and nulliparity have been identified as risk factors for the disease.
Uterine serous carcinoma
Uterine serous carcinoma is an uncommon form of endometrial cancer that typically arises in postmenopausal women.
Despite the name, it is a cancer of the endometrium, which is the inner layer of the uterus; and not of the serous membrane that forms the outer layer of the uterus. The name arises from its histological similarity to serous ovarian cancer.
It is typically diagnosed on endometrial biopsy, prompted by post-menopausal bleeding. Unlike the more common low-grade endometrioid endometrial adenocarcinoma, uterine serous carcinoma does not develop from endometrial hyperplasia and is not hormone-sensitive. It arises in the setting of endometrial atrophy and is classified as a type II endometrial cancer.