The patient proceeded to left upper lobe wedge resection.
MACROSCOPIC DESCRIPTION: "Left upper lobe tissue": A wedge of lung 88x28x20mm stapled at one long margin. Sectioning reveals an ill circumscribed cream coloured lesion 20 mm in dimension. It is at least 5mm from the stapled resection margin.
MICROSCOPIC DESCRIPTION: Sections reveal a mucinous adenocarcinoma showing an entirely lepidic mode of spread with no evidence of invasion. The lesion extends to within <1mm of the pleural surface but there is no breach of the pleural surface. The resection margin is 5mm from the lesion.
DIAGNOSIS: Non-invasive mucinous adenocarcinoma (formally termed bronchioloalveolar carcinoma).