Interstitial fluid pressure of thymic epithelial tumours.

Tumours show an increased interstitial fluid pressure, which correlates with various pathophysiological features. Moreover, interstitial fluid pressure is a prognostic factor for cervical and lung cancer. However, there have been no reports on the usefulness of measuring interstitial fluid pressure in thymic epithelial tumours. Therefore, this study aimed to examine the relationship between interstitial fluid pressure and the clinicopathological characteristics of thymic epithelial tumours. Interstitial fluid pressure was prospectively measured at the centre of the tumour using a 1-Fr Mikro-Tip sensor catheter in 44 patients with thymic epithelial tumours, 40 with thymomas and 4 with thymic carcinomas. Data from these 44 patients were analysed for correlations between interstitial fluid pressure and clinicopathological and demographic factors including sex, age, tumour size, World Health Organization histological subtypes, myasthenia gravis, capsular invasion, mediastinal pleura invasion, lung invasion, pericardium invasion, dissemination, Masaoka-Koga stage, maximal standardized uptake value and recurrence-free survival (RFS). The mean interstitial fluid pressure was 11.3 mmHg; interstitial fluid pressure was significantly correlated with maximal standardized uptake value, lung invasion, dissemination and Masaoka-Koga stage. Low interstitial fluid pressure (≤14 mmHg) showed a tendency for better RFS compared with high interstitial pressure (P = 0.053). Lung invasion, dissemination and Masaoka-Koga stage were correlated with RFS in univariable analysis; lung invasion was selected as an independent prognostic factor in multivariable analysis. On the basis of these results, interstitial fluid pressure of thymic epithelial tumours has been shown to correlate with their clinicopathological features.