Serous tumours are part of the surface epithelial-stromal tumour group of ovarian neoplasm

Ovarian cancer

Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....

s.
They are common neoplasms with a strong tendency to bilaterality, and they account for 50% of all ovarian tumours.
Sixty percent are benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

, 10% are borderline and 30% are malignant

Malignant

Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...

.

Explanation

Benign serous tumours are unilocular (have one lobe); however if very large may be multilocular, contain clear fluid and have a smooth lining composed of columnar epithelial cells with cilia. Surgery is curative.
In borderline lesions, the cyst or surface is lined by papillary structures, which are often very complex. Surgery is usually curative.
Microscopically

Microscope

A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

, stromal papillae are covered by atypical epithelial cells, but stromal invasion is absent, nuclear stratification is present.
Malignant serous tumours are solid, may be cystic and often show haemorrhage and necrosis

Necrosis

Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

. They are lined by a complex papillary pattern with presence of nuclear anaplasia.
Serous carcinomas often have bulky peritoneal

Peritoneum

The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...

 and omental

Omentum

Omentum may refer to:* greater omentum* lesser omentum...

 metastases, and spread to the lymph node

Lymph node

A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...

s is frequent.

Unsurprisingly, 5-year survival decreases as the stage increases.
There is a 25% survival rate

Survival rate

In biostatistics, survival rate is a part of survival analysis, indicating the percentage of people in a study or treatment group who are alive for a given period of time after diagnosis...

with a stage III serous carcinoma.
Staging:

Stage I - Tumour growth limited to ovaries.
Stage II - Growth involving one or both ovaries with pelvic extension.
Stage III - Tumour involving one or both ovaries with implants outside pelvis.
Stage IV- Tumour involving one or both ovaries with presence of distant metastasis.