IM13.11-12 | Cancer Diagnostic Testing — Summary & Reflection

KEY TAKEAWAYS

CBC interpretation in cancer: microcytic hypochromic anaemia in a patient >40 years = exclude GI malignancy (FOBT + endoscopy); leucoerythroblastic film = bone marrow infiltration (biopsy); mature lymphocytosis + smear cells = CLL (flow cytometry); blasts with Auer rods = AML (urgent haematology).

FOBT/FIT: positive test in a symptomatic patient mandates colonoscopy directly — not a gatekeeper. False-positive guaiac FOBT avoided by FIT (human haemoglobin-specific).

PSA: drawn BEFORE DRE; normal <4 ng/mL; grey zone 4–10; >10 = biopsy. Modifiers: PSA velocity >0.75/yr; density >0.15; free:total <10% = cancer-likely. Double PSA value in patients on 5-alpha-reductase inhibitors.

CXR in cancer: spiculated upper lobe mass = lung cancer until CT-proven; bilateral hilar adenopathy = sarcoidosis vs. lymphoma; unilateral pleural effusion = malignant until exudate cytology proves otherwise. Light's criteria for exudate.

Mammography BIRADS: 1–2 = benign; 3 = 6-month follow-up; 4–5 = biopsy. Spiculated mass + microcalcifications (pleomorphic linear) = highest malignancy suspicion.

Biopsy types: FNAC = cells only; core needle = tissue architecture + IHC; excisional = complete lesion (melanoma staging by Breslow thickness). Tissue diagnosis mandatory before treatment in all cancers except radiologically classic HCC in cirrhosis.

Tumour markers: AFP (HCC/testicular), β-hCG (GTN/testicular), PSA (prostate), CA 125 (ovarian monitoring), CEA (colorectal monitoring), CA 19-9 (pancreatic monitoring), LDH (lymphoma prognosis). None reliable for population screening except AFP in cirrhosis surveillance.

REFLECT

Consider the diagnostic journey of Patient C — a 55-year-old smoker who came in for cough. Her CXR showed an opacity that triggered CT, then biopsy, then molecular testing. From a 'routine chest X-ray' she moved in days to a diagnosis of EGFR-mutated lung adenocarcinoma with a targeted therapy available. Without the systematic interpretation of the CXR finding and the decision to biopsy, this would have been attributed to 'chronic bronchitis'. Reflect on the role of the general physician as the entry point to oncological diagnosis: how do you ensure that a concerning radiological finding does not get lost in the system? What safety-netting communication would you use with this patient as you awaited biopsy results? And how does knowing the molecular profile change not just the treatment but the conversation about prognosis?