Lung small cell carcinoma have mutations in...

• A. p63/p40
• B. CK20/Napsin
• C. histone modifier genes PTEN and FGFR1
• D. all of the above

Answer: (C)

Lung small cell carcinoma has a genetic landscape shaped by changes in chromatin remodeling and histone modification pathways, rather than by markers of other lineages. This means alterations in genes that regulate how DNA is packaged and how genes are turned on or off are common in this cancer. That helps explain why a choice referring to histone modifier genes is the best fit: it aligns with the idea that epigenetic regulation is disrupted in SCLC.

Markers like p63/p40 are associated with squamous differentiation, and CK20/Napsin are typically used to identify other lung cancer subtypes; they don’t reflect the characteristic genetic backing of small cell carcinoma. While TP53 and RB1 mutations are hallmark features of SCLC and epigenetic regulators can be involved, emphasizing chromatin-modifying pathways captures the pattern of alterations more than the lineage-specific markers.