Malignant ascites occurs most often in patients with high-grade serous papillary ovarian cancer at initial diagnosis: a retrospective analysis of 191 women treated at Bayreuth Hospital, 2006-2015.

BACKGROUND: Malignant ascites often develops in patients with ovarian cancer, but there is a lack of more detailed characterization of the different histological subtypes.

METHODS: Ascites specimens from patients with ovarian cancer who were treated at Bayreuth Hospital from 2006 to 2015, with follow-up until December 2016, were reevaluated retrospectively.

RESULTS: A total of 191 women (mean age 64 years, range 48-79) were included, of whom 180 (94.2%) had carcinoma, three (1.6%) had malignant mixed müllerian tumors (MMMTs), four (2.1%) had sex cord-stromal tumors (SCSTs), three (1.6%) had germ cell tumors (GCTs), and one (0.5%) had a sarcoma. The carcinoma group comprised 134 (70.1%) patients with high-grade serous papillary ovarian cancer, 17 (8.9%) with low-grade serous papillary ovarian cancer, 10 (5.3%) with mucinous carcinomas, nine (4.7%) with endometrioid carcinomas, six (3.1%) with clear cell carcinomas, and four (2.1%) with neuroendocrine tumors. The latter group consisted of two patients with mixed neuroendocrine-nonneuroendocrine tumors (MiNENs), one with only a small cell carcinoma (SCCO), and one with a mucinous carcinoid. The noncarcinomatous group of eight patients (4.2%) included three (1.6%) with Sertoli-Leydig cell tumor and mature cystic teratoma (MCT), one (0.5%) with a granulosa cell tumor, and one with a leiomyosarcoma. A statistically significant difference in the proportion of patients with malignant ascites was observed, at 17.7% (3/17) in those with low-grade serous papillary ovarian cancer and 91.8% (123/134) in those with high-grade serous papillary ovarian carcinomas. In both patients with MiNEN, the glandular tumor cell component was found in the ascites. Tumor cells were found in the ascitic fluid in 50% (5/10) of patients with mucinous ovarian carcinomas, 16.7% (1/6) of those with clear cell carcinomas, and 33.3% (1/3) of those with MMMTs. The two patients (2/3; 66.7%) with neoplastic squamous cell components in MCT and the only patient with a granulosa cell tumor in the SCST group (1/4; 25%) had malignant cell populations in the ascites, whereas patients with endometrioid cell carcinoma and leiomyosarcoma lacked tumor cells in the ascites. The malignant ascites was detected at the initial diagnosis in all 138 (100%) patients with ovarian neoplasms.

CONCLUSIONS: High-grade serous papillary ovarian cancer was the main histological subtype most frequently found in ascites fluid in this series. The significant difference (P < 0.00001) in the malignancy rate in comparison with low-grade serous papillary carcinoma confirms the histological distinction between the two entities. Initial evidence of ovarian cancer in ascites fluid allows correct primary diagnosis in cytology specimens and is important for staging and prognosis.