Prognostic significance of percentage of bronchioloalveolar pattern in adenocarcinomas of the lung

Bronchioloalveolar (BA) carcinoma of the lung is considered to have a better prognosis than that of common adenocarcinomas of the lung. However, a minor component of the BA pattern is common in many lung adenocarcinomas and the criteria for designating an adenocarcinoma as BA are not well defined. We assessed the clinicopathologic features of 238 cases of lung adenocarcinoma with a partial or predominant BA pattern. Tumors were classified as BA if more than 75% of the tumor had a BA growth pattern. In other words, the tumor grew along pre-existing lung structures without invasion or destruction of parenchyma. Tumors with 50% to 75% BA pattern were considered mixed and tumors with less than 50% BA pattern were designated as solid/acinar (S/A). Fixed, paraffin-embedded tissue sections of each neoplasm were also assessed using immunohistochemical methods with a panel of antibodies specific for p53, retinoblastoma protein, p16, cyclin D1, and cyclin E, and the results were correlated with clinical and pathologic parameters. Our results show that the 5-year survival rate of patients with BA and mixed tumors, 63% and 60%, respectively, was significantly better than that of patients with S/A tumors (P = .026). Patients with BA tumors were more frequently women (55.9%) compared with patients with mixed (48.3%) and S/A (43.8%) tumors. Bronchioloalveolar and mixed tumors were similarly associated with tobacco use, 88.2% and 85%, respectively; slightly less than S/A tumors (93.8%). Clinical and pathologic parameters did not correlate with immunohistochemical results. In conclusion, patients with BA or mixed tumors have similar 5-year survival, better than that of patients with S/A tumors, suggesting that adenocarcinomas can be designated as BA when at least 50% of the tumor has a BA pattern.