While liquid biopsies are a valuable, less invasive tool, a negative result is inconclusive for ruling out actionable mutations in NSCLC. It may simply mean the tumor isn't shedding enough DNA. Therefore, a negative liquid biopsy should never be the final word; it must be followed by a tissue biopsy to ensure patients don't miss out on targeted therapies.

In community SCLC care, molecular strategies are not monolithic. Genomic alteration testing (NGS) is ready for immediate use and can identify targets today. In contrast, neuroendocrine subtyping is still investigational and not yet clinically actionable, pending results from research studies.

In NSCLC, "HER2 positive" can mean one of three largely separate conditions: rare exon 20 mutations (~2%), rare gene amplifications (~2%), or more common protein overexpression (20-30%). Understanding these distinctions is critical for accurate biomarker testing and selecting appropriate therapies.

Clinicians ordering "NGS for lung" often misunderstand that Next-Generation Sequencing alone does not cover all actionable biomarkers, such as PD-L1 or HER2. This requires pathologists to interpret the clinician's intent and order a more comprehensive and appropriate test panel.

While Next-Gen Sequencing (NGS) provides genetic data, IHC directly measures the protein, is faster, cheaper, and requires less tissue. This makes it more scalable for routine clinical use, especially with small biopsy samples. High-level IHC loss correlates well with genetic loss seen on NGS.

Unlike breast or lung cancer where a biomarker's effectiveness persists across treatment stages, biomarkers in upper GI cancers often fail to show similar efficacy when moved from one line of therapy to another. This suggests a more variable and rapidly changing tumor biology.

Contrary to its traditional monolithic treatment approach, SCLC is now understood to have distinct transcriptomic subsets (e.g., ASCL1, NeuroD1). The future of SCLC therapy will likely involve biomarker testing to match patients with the most effective treatments for their specific subtype, mirroring the personalized approach in non-small cell lung cancer.

The primary site of a neuroendocrine neoplasm offers strong diagnostic clues. For example, tumors in the esophagus or gallbladder are almost always poorly-differentiated NECs, while those in the mid-colon are also typically NECs. This site-specificity serves as a powerful diagnostic heuristic for clinicians.

While Next-Gen Sequencing (NGS) can detect PTEN genetic loss, Immunohistochemistry (IHC) is often more practical for routine clinical use. IHC directly measures protein loss, requires less tissue, is faster, more affordable, and highly scalable.