The WHO 2021 classification of lung adenocarcinoma recognizes lepidic, acinar, papillary, micropapillary, and solid patterns. Which pattern carries the WORST prognosis?
- A Micropapillary ✓
- B Lepidic
- C Acinar
- D Papillary
Explanation
Micropapillary pattern in lung adenocarcinoma is characterized by small papillary tufts of tumor cells lacking fibrovascular cores, floating within alveolar spaces. It is strongly associated with lymphovascular invasion, lymph node metastasis, pleural spread, and the worst prognosis among all patterns. Lepidic pattern (non-invasive, cells growing along existing alveolar framework) carries the best prognosis and corresponds to minimally invasive adenocarcinoma. Acinar and papillary patterns have intermediate prognoses. Grade of adenocarcinoma (WHO 2021 Grade 1/2/3) is now determined by the predominant pattern.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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