Small Cell Ovarian Cancer

Small cell ovarian cancer was first described in 1979. It is the rarest sub-type of ovarian cancer, with an incidence rate of <1% of all ovarian cancers. There are two main sub-types of small cell: the pulmonary type (small cell carcinoma of the ovary, pulmonary type (SCCOPT)), and the hypercalcemic type (small cell carcinoma of the ovary, hypercalcemic type, (SCCOHT)). Small cell ovarian cancer is often aggressive

Hypercalcemic Type (SCCOHT) 

Occurs in younger women and tends to have a poor long-term prognosis, although there have been some very hopeful cases. The average age at diagnosis is 24 years old. About two thirds of women and people with small cell ovarian cancer will have associated hypercalcaemia (raised calcium levels). 

The tumours are solid, fleshy, and cream-coloured, about half of them show extraovarian involvement at laparotomy (which is a surgical incision into the abdomen)

Dr Robert Scully initially discovered small cell ovarian cancer nearly three decades ago. Approximately 400 cases have been reported since then. 

The symptoms usually include abdominal discomfort and/or bloating; some people had no symptoms and were found by being examined due to their family history of this type of cancer. Some of the symptoms that people have relate to the hypercalcemia (raised calcium levels); such as severe pancreatitis and having an altered mental state. 

There are some clues which help with the diagnosis of small cell cancer. First, women and people with ovaries affected are young. About 92% of them are diagnosed between 10 and 40 years old. Secondly, calcium levels are raised in about 62% patients. 

Treatment for small cell hypercalcemic type:

Recent research has shown that a multi approach to treatment with surgery, high dose multi-agent chemotherapy, possible stem cell transplant and radiotherapy, is a good option for the treament of this type of ovarian cancer.  As the majority of people diagnosed are younger, you may wish to discuss fertility preserving treatment with your clinical team, they can advise you on whether this may be possible for you, depending on your cancer and how much it has progressed.

What causes small cell hypercalcemic type

Recent studies have suggested that small cell ovarian cancer, hypercalcemic type, is characterised by alterations on the SMARCA4 gene- either germline or somatic (that’s passed down from your family, or not being passed down and occurring randomly). These genetic alterations are found in a variety of other cancers including epithelial carcinoma and mesenchymal neoplasms. 

Pulmonary Type (SCCOPT) 

Small cell ovarian cancer of the pulmonary type is less common than the hypercalcemic type, with an incidence of <1%. It usually occurs in perimenopausal or postmenopausal women and people with ovaries. This type of tumour is usually aggressive and tends to have a poor prognosis.  

Women and people diagnosed with this type of tumour have been aged between 28 and 85 years old, but the average age is 59. 

The tumours resemble small cell carcinoma of the lung, and it is important for the lungs to be checked in case of metastatic tumours (tumours that have spread).

Only 22 cases of small cell ovarian cancer pulmonary type have been described in literature, with the majority of these happening in mature cystic teratomas (a different type of tumour, usually benign, that affects the ovary). 

Usually, it isn’t combined with hypercalcaemia and 45% of patients have only one ovary affected (unilateral). Tumour sizes range from around 4.5 to 26 cm, with an average of 13.5 cm. They are mostly solid, and sometimes can be cystic (filled with fluid).  

Treatment options for small cell pulmonary type:

Due to the small numbers and lack of research, there isn’t a clear consensus on the best type of treatment for these tumours. 

Usually they are treated with surgery, similar to epithelial ovarian cancer (the most common sub-type of ovarian cancer). The usual methods of clinical examination, measuring tumour markers, scanning and imaging are important. Patients who are found to be suitable for debulking surgery (to remove the ovaries, fallopian tubes, womb, cervix, nearby lymph nodes and the fatty layer around the organs called the omentum), should be referred to a gynaecological oncology centre and this should be offered as the treatment of choice. 

Generally, combination chemotherapy will be offered, carboplatin and etoposide, which is the commonly used combination chemotherapy used to treat small cell lung cancer and extrapulmonary uterine and cervical gynaecological small cell cancers. Although there isn’t much research into the success of this chemotherapy regime in small cell ovarian cancer pulmonary type.