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Small cell carcinoma of the ovary (SCCO), also called small cell ovarian cancer, is a very rare form of ovarian cancer. SCCO accounts for 0.1 percent of all ovarian cancers. This cancer is primarily diagnosed in young women, with an average age of 23 at the time of diagnosis. SCCO is aggressive and fast-growing. Early diagnosis and intervention can help achieve the best treatment outcomes.
The ovaries are part of the female reproductive system and are involved in producing eggs. Three types of cells make up the ovarian tissue: epithelial cells, germ cells, and stromal cells. Small cell ovarian cancer arises from abnormal cellular growth, though it’s still unknown which type of cell forms the cancer.
Two-thirds of people with SCCO have hypercalcemia, or high levels of calcium in the blood. When someone has SCCO with hypercalcemia, the disease is called small cell carcinoma of the ovary, hypercalcemic type (SCCOHT). SCCOHT is the most common type of SCCO.
Other people may have different subtypes of SCCO. The neuro-endocrine type is a very rare form of SCCO that also affects young people. The pulmonary type is more common in people who’ve gone through menopause.
One of the primary risk factors for all forms of ovarian cancer is having a mutation in the BRCA1 or BRCA2 gene. These genes are strongly linked to both breast cancer and ovarian cancer. A family history of either breast cancer or ovarian cancer is also associated with an increased risk of ovarian cancer.
Other risk factors include:
Certain factors are associated with a decreased risk of ovarian cancer. For example, pregnancy and breastfeeding are thought to lower the risk of ovarian cancer because they prevent ovulation. People who take birth control pills are also less likely to be diagnosed with ovarian cancer.
SCCO causes similar symptoms to other types of ovarian cancer. These symptoms include:
Symptoms of ovarian cancer are subtle symptoms that can be caused by many different conditions, which can make diagnosis tricky. If you experience a sudden and constant onset of symptoms, see your health care provider promptly to explore a possible diagnosis.
To assess the possibility of ovarian cancer, a doctor will usually start with a pelvic exam to check for enlarged ovaries. The doctor may also check for ascites, which is buildup of fluid in the abdomen and a potential sign of cancer. If the initial physical exam shows evidence of ovarian cancer, you may be referred to a gynecologic oncologist — a doctor who specializes in cancers of the female reproductive system. This doctor may then order several more procedures to confirm a diagnosis.
An ultrasound is a procedure that creates an image using sound waves. An ovarian cancer diagnosis typically involves a transvaginal ultrasound, in which a trained technician inserts a wand into the vagina to produce images of the reproductive organs. An ultrasound can reveal enlarged ovaries, ovarian tumors or cysts, or fluid in the abdomen.
A blood test can take a variety of measurements, including levels of red blood cells, white blood cells, and platelets, which may be high or low in cancer. A blood test can also be used to measure blood calcium levels and detect hypercalcemia. Blood can be tested for the presence of CA-125, a protein made by ovarian cancer cells. High levels of lactate dehydrogenase, a protein that can indicate tissue damage, may also be shown by a blood test.
A biopsy involves obtaining a sample of tissue for analysis, usually by surgical removal of the ovarian tumor. Once removed, the tissue sample undergoes different lab tests to help your doctor confirm or rule out a cancer diagnosis.
Immunohistochemistry (IHC) is a laboratory technique that uses proteins called antibodies to detect molecules present in certain cells. IHC is useful for detecting and visualizing cancer cells in a tissue sample. IHC may be used to analyze biopsied tissue and determine whether a case of ovarian cancer is small cell carcinoma of the ovary or another subtype.
X-rays use radiation to take images of bones and tissues. CT scans use multiple X-rays to create more detailed images. CT scans are often used to check for tumor cells in other parts of the body to confirm whether the ovarian cancer has metastasized (spread). A standard chest X-ray may be used to check for cancer cells or fluid around the lungs caused by metastasis.
A laparoscopy is a minimally invasive surgical procedure. To perform a laparoscopy, a doctor makes a small cut in the abdomen and inserts a thin tube with a light. This procedure allows for internal visualization of the ovaries and other abdominal organs. It can also help the doctor determine whether the disease has spread.
Because ovarian cancer is associated with certain genetic mutations, your doctor may recommend genetic testing to identify whether you have a relevant gene mutation. The BRCA1 and BRCA2 genes are often examined due to their importance in ovarian cancer. SCCOHT is linked to mutation in another gene called SMARCA4. A genetic test for a SMARCA4 mutation can help support a diagnosis of small cell ovarian cancer.
Following diagnosis of SCCO, your health care provider will typically go over your treatment options so you can decide on a treatment plan together. Whenever possible, treatment for SCCO should be carried out or overseen by a gynecologic oncologist.
Visible tumors in the ovaries or other organs (if the cancer has metastasized) may be surgically removed. The goal of surgery is tumor debulking, or removal of as much of the tumor as possible, to improve the outcome of subsequent treatments.
Your doctor may also recommend an oophorectomy (removal of an ovary) or hysterectomy (removal of the uterus). However, because SCCO primarily affects young people of childbearing age, these procedures may sometimes be avoided to help preserve fertility.
Most people with SCCO will be treated with chemotherapy in an attempt to kill the remaining cancer cells after tumor debulking. A commonly used treatment regimen known as BEP is a combination of three different chemotherapeutic drugs: Blenoxane (bleomycin), Toposar (etoposide), and Platinol (cisplatin). Paraplatin (carboplatin) functions similarly to cisplatin and may also be used to treat SCCO.
Chemotherapy may be administered as adjuvant therapy (following surgery) or as neoadjuvant therapy (before surgery).
Radiation therapy, or radiotherapy, is not used as widely as chemotherapy to treat SCCO. Radiation may be used in some cases to shrink tumors that are resistant to chemotherapy.
Due to how rare SCCO is, there is not yet a standard treatment approach. However, there are ongoing clinical trials to find new, effective therapies against SCCO. The antibody drug Keytruda (pembrolizumab) is currently being evaluated as a potential therapy against SCCO. If you’re interested in participating in a clinical trial, talk with your doctor about what’s available to you.
SCCO is generally resistant to treatment, and most people die within two years of diagnosis. To improve the survival rate of people with SCCO, early diagnosis is crucial — people diagnosed with early stage disease (before the cancer has spread) can get treated sooner and have longer survival. People with SCCO may also be encouraged to participate in clinical trials to help identify better treatments.
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Howard Goodman, M.D. is certified by the American Board of Obstetrics and Gynecology and specializes in the surgical management of women with gynecologic cancer. Review provided by VeriMed Healthcare Network.. Learn more about him here.
Aminah Wali, Ph.D. received her doctorate in genetics and molecular biology from the University of North Carolina at Chapel Hill. Learn more about her here.
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