Relevance of Intraoperative Pleural Lavage Cytology and Histologic Subtype in Lung Adenocarcinoma.

BACKGROUND: The association between pleural lavage cytology (PLC) and histologic subtype remains unknown. In this study, we evaluated the effect of a micropapillary pattern (MPP) in lung adenocarcinomas on results of PLC. METHODS: We retrospectively reviewed 600 consecutive patients with surgically resected pulmonary adenocarcinomas and investigated the relationship between PLC status and clinicopathologic factors, including a histologically identified MPP component. RESULTS: PLC was positive in 25 patients (4.2%). Positive PLC was significantly associated with MPP (p = 0.0001), lymph node metastasis (p = 0.01), and pleural invasion (p < 0.0001) according to multivariate analysis. Furthermore, the presence of MPP reinforced the effect of some established predictive factors, such as large tumor size, lymph node metastasis, pleural invasion, and lymphovascular invasion, on positive PLC. Two factors-MPP and positive PLC-were associated with a higher incidence of occult N2 lymph node metastases. The prognosis of adenocarcinomas in patients with MPP or positive PLC was significantly worse than that of patients without these features. Furthermore, the survival of MPP and positive PLC group (MPP+ PLC+) was significantly worse than that of MPP and negative PLC group (MPP+ PLC-, p = 0.03). CONCLUSIONS: The presence of MPP in lung adenocarcinoma can be an independent predictor of positive PLC. These two factors have complementary and synergistic roles as prognostic factors. Detailed preoperative or intraoperative examination of histologic subtype and PLC findings may provide important information for prediction of tumor progression and decisions regarding the surgical procedure.