Pathological N1/N2 in Clinical Stage I Bronchogenic Carcinoma. Analysis From a Prospective Multicentre Database Alejandra Romero Román; Silvana Crowley Carrasco; Mariana Gil Barturen; Ana Royuela; Carme Obiols; Sergi Call; José Luis Recuero; Íñigo Royo; Raúl Embún; David Gómez de Antonio;