Objective: In the staging of lung cancer, pleural effusion that is malignant on cytologic examination is regarded as T4 disease, and curative resection cannot be performed. We conducted this study to determine whether cancer cells can be present in the pleural cavity with no pleural effusion, to investigate the factors contributing to that occurrence, and to evaluate its prognostic significance.
Methods: Eighty-five patients (77 males, eight females) with a median age 60.1-+/--7.9 years (31--74 years) underwent a major lung resection, due to lung cancer in our department. From January 1998 to December 1999, 30 pneumonectomies, seven bilobectomies, 46 lobectomies and two wedge-resections were performed. Chest wall resection was performed in four patients. After performing a posterolateral thoracotomy and lung resection with extended mediastinal lymph node dissection, the pleural cavity was filled with 1 l physiologic saline solution (PSS) and the fluid was shaken. The lavage fluid was suctioned off (S1). Immediately after the lavage, the pleural cavity was refilled with 3 l PSS. The surgeon washed out the pleural cavity by hand for 1 min and the fluid was suctioned off. Finally, the pleural cavity was refilled with 1 l PSS and a new lavage fluid was suctioned off (S2). A cytologic examination was carried out for each sample.
Results: The pathology report showed 39 adenocarcinomas, 33 squamous-cell, two adenosquamous, four large-cell, two neuroendocrine and five undifferentiated carcinomas. S1 was positive in eight patients (9.4%), while S2 was positive in four patients (4.7%). The correlation of positive pleural lavage and infiltrated lymph nodes demonstrated a statistically significant relation between presence of N2 disease and positive S2 sample (P = 0.049). No significant correlation existed between positive lavage sample (S1 or S2) and TNM stage, level of T, extent of tumor invasion, kind of operation, histological type or differentiation of the cancer (Chi square test). The mean follow-up is 11.3 +/- 6.2 months (4--22 months). There are 78 patients alive. A significance difference in survival was identified in-patients with positive S1 (P = 0.0081), and positive S2 (P = 0.0251) (Kaplan--Meier).
Conclusion: The cytologic results of lavage were positive for malignant cells in eight of 85 patients (9.4%). The existence of cancer cells in the pleural cavity can be the result of their exfoliation or surgical manipulations. The mechanical irrigation subdivides the percentage of positive samples. Our study supports that the positive findings on pleural lavage cytology is an essential prognostic factor.