The percentage of lepidic growth is an independent prognostic factor in invasive adenocarcinoma of the lung

BACKGROUND: The literature is inconclusive as to whether the percentage of the lepidic component of an invasive adenocarcinoma (AC) of the lung influences prognosis. We studied a population-based series of selected, resected invasive pulmonary ACs to determine if incremental increases in the lepidic component were an independent, prognostic variable. METHODS: Patients undergoing resection for lung cancer reported to the Cancer Registry of Norway and diagnosed in the period 1993-2002 with a bronchioloalveolar carcinoma (BAC) (old terminology) (adenocarcinoma in situ, AIS in the new terminology) in the lung were selected. A pulmonary pathologist reviewed all sections and estimated the percentage of the lepidic component. Follow-up of survival was to the end of 2013. RESULTS: One hundred thirty-one patients were identified, 102 had AC with lepidic growth. Of these, 44 had AC with a component of lepidic growth less than 50 % and seven had AC with 95 % lepidic component or more. One of the latter cases was considered to be AIS. In regression analyses, superior survival was associated with a greater lepidic component (p = 0.041). Mucinous tumors had a worse prognosis than non-mucinous (p = 0.012) in regression analyses, as did increasing age and stage. The five-year observed survival was 69.0 % for non-mucinous cases and 66.7 % for the group with a lepidic component of 80 % or greater. CONCLUSION: The percentage of the lepidic component appears to be an independent, significant prognostic factor in a selection of pulmonary AC.