Primary squamous cell carcinoma of the ovary accompanied by transition of a mucinous borderline ovarian tumor

This report describes a woman with a rare primary squamous cell carcinoma of the ovary accompanied by transition of a mucinous borderline ovarian tumor. A woman in her late 40s was referred for abdominal discomfort, which worsened during defecation. Pelvic magnetic resonance imaging showed a multiloculated cystic lesion in the left adnexa measuring approximately 7.5 × 9.5 × 7.0 cm. An intraoperatively obtained frozen biopsy sample of the mass in the left ovary was positive for malignancy, resulting in a surgical staging operation. The tumor was composed of squamous cell carcinoma and mucinous borderline tumor. There was no evidence of capsular invasion or invasion of other internal organs, including pelvic and para-aortic lymph nodes (0/41). Immunohistochemistry showed that the tumor was diffusely positive for cytokeratin 7, cytokeratin 20, Ki-67, and P40 but negative for P16. After a debulking operation, the patient has been monitored regularly without adjuvant therapy owing to final surgical staging of the tumor as stage IA.