Normal size ovarian cancer syndrome (NOCS) is a challenge for clinicians regarding timely diagnosis and management due to atypical clinical and imaging features. It is extremely rare with only a few cases reported in the literature. More data are needed to clarify its biological behavior and compare the differences with abnormal size ovarian cancer.

To assess the clinical and pathological features of NOCS patients treated in our institution in the last 10 years and to explore risk factors for relapse and survival.

Patients who were pathologically diagnosed with NOCS between 2008 and 2018 were included. Papillary serous ovarian carcinoma (PSOC) patients were initially randomly recruited as the control group. Demographics, tumor characteristics, treatment procedures, and clinical follow-up were retrospectively collected. Risk factors for progression-free survival and overall survival were assessed.

A total of 110 NOCS patients were included; 80 (72.7%) had primary adnexal carcinoma, two (1.8%) had mesotheliomas, 18 (16.4%) had extraovarian peritoneal serous papillary carcinoma, and eight (7.3%) had metastatic tumors. Carbohydrate antigen (CA)125 and ascites quantity were lower in the NOCS cohort than in the PSOC group. The only statistically significant risk factors for worse overall survival (P < 0.05) were the levels of CA199 and having fewer than six chemotherapy cycles. The 1-year, 3-year, and 5-year survival rates were 75.5%, 27.7%, and 13.8%, respectively.

The clinical symptoms of the NOCS group are atypical, and the misdiagnosis rate is high. Ascites cytology and laparoscopic exploration are valuable in the early diagnosis to avoid a misdiagnosis. The level of CA199 is the most important predictor of overall survival, and more than six cycles of chemotherapy contributes to the increased survival rates of NOCS patients.

• Normal-sized ovarian carcinoma syndrome
• Ovarian cancer
• Survival
• Prognostic factors
• Epithelial ovarian carcinomas
• Carbohydrate antigen 125