Clinical implication of microscopic anthracotic pigment in mediastinal staging of non-small cell lung cancer by endobronchial ultrasound-guided transbronchial needle aspiration

Microscopic anthracotic pigment (MAP) is frequently observed in endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) specimen in non-small cell lung cancer, but its clinical interpretation is not well-known. The aim of this study was to evaluate the clinical implication of MAP in mediastinal staging of non-small cell lung cancer. From May 2010 to July 2011, consecutive potentially operable non-small cell lung cancer patients who underwent EBUS-TBNA for mediastinal staging were recruited. Of the total 133 patients, 102 (76.7%) were male patients. Median age was 68 yr. Total 279 mediastinal lymph nodes were sampled by EBUS-TBNA; station 4R (100, 35.8%) and station 7 (86, 30.8%) were the most common sites. Malignant lymph nodes were 100 (35.8%). MAP was observed in 61 (21.7%) lymph nodes, and among them only 3 were malignant lymph nodes (P < 0.001). The lymph nodes with MAP were smaller (9.0 vs 10.8 mm, P = 0.001) and showed low standard uptake values on FDG-PET (4.4 vs 4.7, P = 0.256). In multivariate analysis, MAP was negatively associated with malignant lymph node (adjusted OR, 0.12; 95% CI, 0.03-0.42; P < 0.001). In potentially operable non-small cell lung cancer patients, MAP in endobronchial ultrasound-guided transbronchial needle aspiration specimens is strongly associated with benign mediastinal and hilar lymph nodes.