LAUSR

Background Primary ovarian serous carcinomas (OSC) with extensive squamous differentiation is a rare, and histological diagnostic criteria and biological behavior have not been fully established. We present an extremely rare case of primary OSC of the ovary with squamous differentiation. Case presentation A 58-year-old (gravidity 3, parity 2) female was admitted complaining of abdominal distention for 6 months. No apparent tumor in the cervix was found by a physical examination. Serum levels of cancer antigen 125 (CA125) was elevated (2723.0 IU/L). Macroscopically, a 7 cm tumor of the left uterine adnexa, a 5 cm tumor of the right adnexa, and a 3 cm tumor of the omentum were found. Histological and immunochemical tests confirmed a diagnosis of OSC with squamous differentiation. Debulking surgery with tumor resection was performed. The patient was subsequently received postoperative chemotherapy. Conclusions In summary, OSC with extensive squamous differentiation is a rare, and the inter- and intratumor heterogeneity may be the reason for this phenomenon. Histological diagnostic criteria and biological behavior have not been fully established because of the limited data.