Cytologic Histotyping of Gynecologic Malignancies in Peritoneal Fluids Is Reliable When Compared to Its Corresponding Surgical Specimen.

backgroundCytologic examination of peritoneal fluid (PTFL) often represents the first and only pathologic specimen available to guide management of gynecologic malignancies (GMs). This study examines the cytohistologic correlation between histotyping of GM in PTFL and its corresponding surgical specimen (SS).

methodsThe study retrospectively identified positive PTFL with a GM between 2017 and 2022. Cytologic specimens (CSs) that were obtained after or concurrently with its diagnostic SS (biopsy/resection) were excluded. Root cause analysis of discordant cases was performed by reviewing morphology, specimen characteristics, and immunophenotype of CS.

resultsGM affected 55.8% (502/899) of malignant PTFL, of which 15.7% (79)/22.3% (112) was the only/initial diagnostic sample, respectively. Compared to SS, when a subtype was rendered on CS (91.9%), the concordance rate is 91.2% (almost perfect agreement, K = 0.842). Factors contributing to incorrect/inadequate subtyping include specimen limitations (low volume and/or cellularity), cytopathologist preference, and insufficient immunophenotyping. In seven patients (1.4%), the CS was able to render a more definitive diagnosis than its preceding nondiagnostic SS due to the paucity of lesional cells.

conclusionWhen compared to SS, histotyping of GM in PTFL is reliable and, at times, can be more definitive than its surgical counterpart. In some cases, subtyping is limited by extrinsic factors (i.e., specimen limitations). In other cases, the responsible cytopathologist prefers not to subtype despite supportive morphologic and immunohistochemical features. This highlights an opportunity for improvement in the diagnosis/subtyping of GM in PTFL, which may be the initial or only diagnostic specimen prior to patient treatment.