Cytological diagnosis of dysgerminoma associated with pregnancy via peritoneal effusion analysis: a case report.

Background: Dysgerminoma, a uncommon malignant neoplasm originating from primitive ovarian germ cells, is exceptionally rare during pregnancy. While several studies have documented dysgerminoma diagnosis via peritoneal effusion cytology, no cases identified during pregnancy have been reported to date. This study presents the first reported case of dysgerminoma diagnosed through peritoneal effusion cytology in a pregnant patient.

Case presentation: A 27-year-old pregnant woman presented to our hospital with an early intrauterine pregnancy and a right adnexal mass detected on B-ultrasound at a local hospital. Cytological evaluation of the peritoneal effusion revealed a polymorphic cell population dominated by discrete large tumor cells mixed with reactive lymphocytes and histiocytes. These tumor cells exhibited moderate to abundant eosinophilic or vacuolated cytoplasm with well-defined borders. Most had round or oval nuclei with high nuclear-to-cytoplasmic (N/C) ratios, granular chromatin with uneven distribution, and distinct nucleoli visible in some cells. While a subset of large cells showed irregular nuclear contours and angular appearances. Immunocytochemistry (ICC) results of cell block (CB) showed positive staining for SALL4, CD117, OCT3/4, PLAP, and D2-40, but negative staining for LCA, CD30, EMA, CK-P, CR, and SF-1. The final diagnosis of dysgerminoma was made by integrating peritoneal effusion cytology, cell block analysis, and ICC results. The patient underwent right adnexectomy and subsequently delivered a healthy female infant at 36 + 4 weeks of gestation. Four-year postoperative follow-up showed no evidence of disease recurrence.

Conclusion: This report describes the cytopathological features of dysgerminoma in peritoneal effusion, specifically the presence of discrete large tumor cells with hyperchromatic nuclei and prominent nucleoli. Cytopathologists should maintain a high index of suspicion for this entity, particularly in young patients, and adopt a comprehensive diagnostic approach including cytomorphological assessment, CB examination, and immunocytochemical analysis to make an accurate diagnosis.