Neuroendocrine neoplasms of the ovary: an analysis of clinicopathological characteristics and prognosis with a focus on histological grading

Objective Ovarian neuroendocrine neoplasm is a rare and highly heterogeneous neoplasm. This study is aimed to describe its demographic and clinicopathological features and identify its prognostic factors. Methods Clinical data of 399 patients diagnosed with ovarian neuroendocrine neoplasms between 2004 and 2016 in the Surveillance, Epidemiology, and End Results (SEER) database were analysed retrospectively. Survival curves were drawn using the Kaplan-Meier method, comparisons among different subgroups were evaluated using log-rank tests, and multivariate Cox regression analyses identified independent prognostic factors. Results The five-year survival rates of patients with different histological types (carcinoid tumour, neuroendocrine carcinoma and special type of carcinoid tumour) were 25.5%, 96.1% and 75.0%, respectively (P < 0.001). Multivariate Cox analysis revealed that in carcinoid tumours, advanced FIGO stage was the only predictor. Additionally, no significant difference was observed among stages II, III and IV using the log-rank test. In neuroendocrine carcinoma, an advanced FIGO stage and high-grade differentiation were risk factors, while chemotherapy was a protective factor. Among all ovarian neuroendocrine neoplasms with a known histological differentiation status, no significant difference was observed among different histological types; only high-grade differentiation was an independent risk factor, and chemotherapy was a protective factor. Conclusions Patients with neuroendocrine carcinomas and carcinoid tumours of an advanced FIGO stage have a poor prognosis. Poor differentiation of neuroendocrine carcinomas indicates a short survival time, and adjuvant chemotherapy appears to be effective. Histological differentiation of ovarian neuroendocrine neoplasms is the most potent prognostic factor comparing to other known factors. Taken together, ovarian neuroendocrine neoplasms might be better classified as low- or high-grade ones rather than the currently used classification based on histological types in the future.