Growth speed in NSCLC varies by patient and is influenced by histologic subtype, tumor genetics, and the immune microenvironment. In general, NSCLC tends to grow more slowly than SCLC, but “slower” does not mean harmless. Certain aggressive variants—such as poorly differentiated tumors—can grow and metastasize faster. Clinically, what matters most is documenting the growth trend through imaging and completing staging workup. Untreated lung cancer carries a high risk of progression, so once a suspicious lesion is identified, timely evaluation (CT, PET-CT, biopsy) and a treatment plan are essential. Speed should be interpreted with data, not assumptions.