CT for detection of malignant posterior intercostal lymph nodes in patients undergoing pre-operative staging for malignant pleural mesothelioma

•Posterior intercostal node (PILN) metastasis portends poor outcome in mesothelioma.•The PILN nodal group has recently been incorporated into the TMN staging system.•CT is not sensitive or specific for detecting PILN metastasis in mesothelioma.•Assessment of PILN nodal status is likely a surgical diagnosis in mesothelioma. Recent evidence suggests that patients with malignant pleural mesothelioma (MPM) undergoing extended pleurectomy/decortication (eP/D) with metastasis to the posterior intercostal lymph nodes (PILN) have a worse prognosis. In this study, we determine if MPM PILN metastasis can be reliably detected on computed tomography (CT). Preoperative staging CT exams were reviewed for the presence of PILN in MPM patients undergoing eP/D between 2007–2013 with surgical sampling of their PILN. CT images were reviewed by two thoracic radiologists blinded to clinical records, including operative pathology reports. The number and short axis size of PILN were recorded and correlated with surgical pathology. Statistical analysis examined the value of preoperative CT to detect metastatic PILN. Of 36 patients that underwent eP/D with PILN sampling had preoperative CT images for review. At surgery, 22 of these patients had metastatic PILN and 14 had benign PILN. The positive and negative predictive values for one or more nodes seen on preoperative CT were 60 % and 38 % respectively. The number of PILN on preoperative CT did not predict metastasis (p = 0.40) with an average of 2 PILN seen, regardless of PILN pathology. The average nodal short axis size was 4.6 mm and 4.8 mm for benign and malignant PILN, respectively, and PILN short axis size did not predict metastasis (p = 0.39). There was little inter-observer variability between the size and number of nodes detected by each radiologist. CT does not reliably identify metastatic PILN on preoperative CT for patients with MPM undergoing extended pleurectomy/decortication.