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There are some rarer types of ovarian cancer that do not come from the epithilial cell, sex cord stromal cell, steroid cell or germ cell. 

Carcinosarcomas (ovarian sarcomas, previously referred to as malignant mixed mullerian tumours [MMMT])


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Although classified as carcinosarcomas, these tumours are similar to epithelial tumour types and sometimes referred to as metaplastic carcinoma. These are treated with a combination of surgery and chemotherapy.

Small cell ovarian carcinoma

There are three main variants of small cell;

  • Small cell ovarian carcinoma pulmonary type (SCOCPT) is extremely rare accounting for less than 0.5 per cent of ovarian cancers diagnosed. 

  • Small cell carcinoma of the hypercalcemic type (SCCOHT)

  • Large cell variant of small cell carcinoma or non-small cell small cell carcinoma (NSCSCC). They are usually treated as aggressive epithelial ovarian carcinomas, not as small cell carcinomas.

    Unfortunately, with so few cases there has been relatively little research into new drugs specifically targeting small cell ovarian cancer. There has been a recent review of cases of small cell ovarian carcinomas which concluded that surgery is appropriate, especially in very early stages of disease, but chemotherapy should be considered.

    Neuro-endocrine carcinomas

    These are extremely rare tumour types and are primarily treated with surgery and may involve chemotherapy and other drugs. There are variants;

    • Non-small cell neuro-endocrine carcinoma (large cell variant) (NSCNEC)

    • Classical primary carcinoid (well differentiated neuroendocrine cancer)

    • Classical carcinoid metastatic from primary gastrointestinal site

    • Atypical carcinoids or high grade neuroendocrine carcinomas can also rarely occur.

      Treatment with somatostatin analogues (drugs which slow down the production of hormones) could help to control symptoms and stabilise these slow-growing tumours.

      Squamous cell carcinoma rising within dermoid cyst/teratoma

      Dermoid cysts are the commonest ovarian tumours but are nearly always benign. However, in rare number of cases (1-2 per cent) can become malignant (cancerous), typically in postmenopausal women. Squamous cell carcinoma (SCC) is the most common type of malignancy that arises and comprises more than 80 per cent (of the 1-2 per cent) of cancers that are seen. They are often diagnosed late due to pressure symptoms or torsion (twisting of the ovary) and the resulting abdominal pain, and usually occur in older women. Surgery is normally sufficient if caught at an early stage. For more advanced stages this may be combined with chemotherapy, however due to the extreme rarity of these tumours the optimal chemotherapy has yet to be defined.

      Woman and friendStruma ovarii malignum

      Struma ovarii is a variant of mature teratomas which contains in excess of 50 per cent thyroid tissue. They account for only three per cent of ovarian teratomas and generally have a low malignant (cancerous) potential and are usually successfully treated with surgery. In younger women conservative fertility sparing surgery can be considered with possible further surgery and completion of the family. Read our younger women section for more information.


      Serous psammocarcinoma is a rare variant of serous carcinoma arising either from ovary or peritoneum. It is usually treated by surgery alone although is some cases chemotherapy will also be used but due to its extreme rarity the optimum therapy is yet to be identified.


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      Last reviewed: May 2016
      Next review: April 2019