Clinical features of bronchioloalveolar carcinoma with new histologic and staging definitions.

Introduction: To assess clinical features of bronchioloalveolar carcinoma (BAC) based on the 1999 World Health Organization Classification ("pure BAC"), compare patients with pure BAC with patients previously diagnosed as BAC not meeting the 1999 definition, and compare survival changes of pure BAC based on the old and new (2009) staging systems.

Methods: A pulmonary pathologist reviewed each BAC tumor diagnosed between January 1, 1997, and December 31, 2007, identifying cases meeting the new criteria. Cases were restaged according to the seventh edition of the tumor, node, metastasis classification introduced in 2009. Patients with pure BAC were analyzed under both staging systems for changes in overall survival estimation.

Results: Of 338 total patients who were diagnosed with BAC, 117 were classified as pure and 221 were non-pure BAC. Seventy-eight of the 117 and 178 of the 221 had no other primary lung cancer. One-year and 5-year survival for the 78 patients with pure BAC were 94.8 and 83.5%, and for the 178 patients were 92.6 and 46.4%, respectively. Restaging for pure BAC cases resulted in nine of the 78 cases (12%) changing stage. Compared with the old staging, patients with advanced stage under the new stage had a worse 5-year survival (53% versus 45%), but no change was observed for stage IA.

Conclusions: For patients with pure BAC, the new pathologic system favorably affects survival and the new staging system may more accurately reflect prognosis in advanced stage cancer. Our results have important implications for researchers, clinicians, and patients.