Ovarian squamous cell carcinoma (oSCC) or squamous ovarian carcinoma (SOC) is a rare tumor that accounts for 1% of ovarian cancers. Included in the World Health Organization's classification of ovarian cancer, it mainly affects women above 45 years of age. Survival depends on how advanced the disease is and how different or similar the individual cancer cells are. Squamous ovarian carcinoma is a recognized but uncommon diagnosis, often originating from a transformation of mature cystic teratoma (MCT). Unlike other squamous cell carcinomas, factors like UV exposure and tobacco use play a less significant role. Chronic inflammation in MCT and human papillomavirus (HPV) infection are linked to its development. The tumor emerges through metaplasia of the ovarian surface epithelium. While MCT is the primary source in most cases, others are associated with endometriosis or Brenner tumor, and rare metastasis from other organs can also lead to squamous ovarian carcinoma. Treatment for oSCC involves surgery, chemotherapy, and radiotherapy, but efficacy of these treatments is unclear. While there is no well-studied chemotherapy regimen for ovarian SCCs, platinum-based chemotherapy is often used. The earliest reported instance of pure primary SCC was by Ben-Baruchet in 1988; oSSC emerging from pre-existing lesions have been recorded since the early 1950s.

Reference
Wiki: Non-epithelial ovarian tumor