Table 2. IASLC/ATS/ERS—2011 classification of lung adenocarcinoma.

Resection specimen based classification

Preinvasive lesions

Atypical adenomatous hyperplasia

Adenocarcinoma in situ

Nonmucinous

Mucinous

Mixed mucinous/nonmucinous

Minimally invasive adenocarcinoma

Nonmucinous

Mucinous

Mixed mucinous/nonmucinous

Invasive adenocarcinoma

Lepidic predominant

Acinar predominant

Papillary predominant

Micropapillary predominant

Solid predominant with mucin production

Variants of invasive adenocarcinoma

Invasive mucinous adenocarcinoma

Colloid

Fetal

Enteric

Biopsy/cytology specimen based classification

Morphologic adenocarcinoma patterns clearly present

Adenocarcinoma, describe identifiable patterns (lepidic, acinar, papillary, micropapillary, solid)

Adenocarcinoma with lepidic pattern (if pure lepidic pattern, to be mentioned that invasive component cannot be excluded on small biopsy/cytology specimen)

Mucinous adenocarcinoma (patterns to be described)

Adenocarcinoma with fetal pattern

Adenocarcinoma with colloid pattern

Adenocarcinoma with (describe patterns) and clear cell features

Adenocarcinoma with (describe patterns) and signet ring features

Morphologic adenocarcinoma patterns not present (possibility of adenocarcinoma suggested by ancillary stains)

‘Non-small cell lung carcinoma, favour adenocarcinoma’

Mention staining methodology used

IASLC, International Association for the Study of Lung Cancer; ATS, American Thoracic Society; ERS, European Respiratory Society.