WHO 2021 classification of lung tumors reclassified adenocarcinoma-in-situ (AIS) and minimally invasive adenocarcinoma (MIA). Which statement is correct regarding AIS per WHO 2021?
- A AIS has ≤5 mm invasive component and is classified as stage IA1
- B AIS shows pure lepidic growth without invasion and measures ≤3 cm, with near-100% 5-year survival after complete resection ✓
- C AIS can be mucinous or nonmucinous; mucinous AIS is associated with KRAS mutation
- D AIS contains a fibrous stroma that can harbor stromal invasion, distinguishing it from atypical adenomatous hyperplasia
Explanation
WHO 2021 defines AIS as a small (≤3 cm) adenocarcinoma with pure lepidic growth (tumor cells growing along pre-existing alveolar walls without architectural destruction or vascular/pleural/airspace invasion). AIS carries near-100% 5-year disease-specific survival after complete surgical resection. Mucinous AIS does exist and is associated with KRAS mutations (option C is partially correct but the full AIS definition in option B is the most complete and accurate for NEET PG purposes). MIA (minimally invasive adenocarcinoma) differs by having ≤5 mm invasive component; AIS has zero invasion. Atypical adenomatous hyperplasia (AAH) is the precursor lesion measuring <5 mm.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.