PA6.4-6 | Tumour Effects, Immunology & Laboratory Diagnosis — Summary & Reflection

KEY TAKEAWAYS

This module has covered the three terminal arcs of neoplasia:

1. Host effects
• Local: compression, obstruction, ulceration/bleeding, superimposed infection.
• Systemic: cachexia (TNF-α/IL-1/IL-6 driven; not simple starvation) and paraneoplastic syndromes (ectopic ACTH in SCLC, SIADH in SCLC, PTHrP-hypercalcaemia in squamous lung Ca, Trousseau/migratory thrombophlebitis in pancreatic Ca, acanthosis nigricans in gastric Ca, HPOA + clubbing in bronchogenic Ca).

2. Tumour immunology
• TSA (neo-antigens) vs TAA (over-expressed normal antigens).
• Immune surveillance via CTLs and NK cells.
• Evasion: antigen loss, TGF-β/IL-10 immunosuppression, PD-L1/PD-1 checkpoint.
• Immunotherapy: checkpoint inhibitors (anti-PD-1/PD-L1, anti-CTLA-4) and CAR-T cells.

3. Laboratory diagnosis
• Tissue: excisional/incisional/core biopsy vs FNAC vs frozen section.
• IHC: lineage (CK→carcinoma; LCA→lymphoma; S100→melanoma/nerve sheath) and predictive markers (ER/PR, HER2, Ki-67, PD-L1).
• Tumour markers: AFP (HCC/germ cell), CEA (colorectal monitoring), PSA (prostate monitoring), CA-125 (ovary), CA19-9 (pancreas), hCG (trophoblastic), calcitonin (MTC).
• Molecular: FISH, PCR, NGS, flow cytometry; companion diagnostics (HER2→trastuzumab; EGFR→erlotinib; BCR-ABL→imatinib).
• Grading (pathologist; differentiation; Grade 1–4) vs Staging (extent; TNM; Stage I–IV) — independent, complementary.

REFLECT

Consider a patient newly diagnosed with advanced cancer who asks you: 'Doctor, are my own immune cells not fighting the cancer?' What would you tell them, in plain language, about how the tumour has outsmarted their immune system — and why immunotherapy might help? Write 3–4 sentences as if speaking directly to this patient. Then consider: what emotional dimension of this conversation would you need to prepare for?