Effects of tumours, paraneoplastic syndromes, tumour markers and cancer in Pakistan

Effects of tumours on the host

Local effects

• Pressure on nearby structures (a pituitary adenoma pressing on the optic chiasm; a brain tumour raising intracranial pressure).
• Obstruction of hollow organs (bowel, bile duct: jaundice from cancer of the head of the pancreas).
• Ulceration and bleeding (colon cancer causing iron-deficiency anaemia; gastric cancer).
• Infection behind an obstruction (pneumonia behind a bronchial cancer).
• Destruction of tissue (pathological fractures from bone metastases).

Hormonal effects

Tumours of endocrine glands, benign or malignant, can produce excess of their normal hormone: insulinoma (hypoglycaemia), phaeochromocytoma (hypertension), pituitary and adrenal adenomas. Well-differentiated tumours are more likely to do this.

Cancer cachexia

Progressive loss of body fat and lean muscle, with weakness, anorexia and anaemia. It is driven mainly by cytokines, especially TNF (also IL-1, IL-6 and proteolysis-inducing factor), not just by reduced intake. Basal metabolic rate stays high.

Paraneoplastic syndromes

Symptoms in cancer patients that cannot be explained by local or distant spread, or by the hormones normally made by the tissue of origin. They may be the first sign of a hidden cancer.

Tumour markers

Tumour markers are substances made by tumours that can be measured in blood or other fluids. They are best for monitoring response to treatment and detecting recurrence; most are not specific or sensitive enough for screening or diagnosis on their own.

Laboratory diagnosis of cancer

• Histology of biopsy or excision specimens: the gold standard. A frozen section gives a quick diagnosis during surgery.
• Cytology: fine needle aspiration cytology (FNAC) of lumps (thyroid, breast, lymph nodes); exfoliative cytology (Pap smear for cervix, sputum, urine, effusions).
• Immunohistochemistry: antibodies identify the cell of origin:

• Molecular tests: BCR-ABL (PCR) in CML, HER2 amplification (FISH), mutation panels.
• Flow cytometry: leukaemias and lymphomas.

Cancer in Pakistan

Pakistan does not yet have a complete national cancer registry, so figures come from hospital-based registries (such as Shaukat Khanum and the Karachi registry) and international estimates such as GLOBOCAN (International Agency for Research on Cancer). Those sources consistently show:

• Breast cancer is the commonest cancer in women, often presenting late and at a younger age than in Western countries.
• Oral cavity cancer is among the commonest cancers in men, linked to betel nut, gutka, naswar and smoking.
• Other common cancers: lung, liver (hepatitis B and C), oesophagus, cervix, colorectal, leukaemia and lymphoma; childhood cancers such as leukaemia and retinoblastoma.

Exact rankings and numbers change between reports, so confirm current figures in the latest GLOBOCAN fact sheet for Pakistan.

Screening and prevention

• Breast: breast self-awareness, clinical breast examination, mammography for women in recommended age groups.
• Cervix: Pap smear or HPV testing; HPV vaccination prevents most cervical cancers.
• Colorectal: faecal occult blood testing, colonoscopy.
• Liver: hepatitis B vaccination, safe injections and blood, treatment of hepatitis C.
• Oral: stopping tobacco, betel nut and naswar; oral examination of high-risk people.

For how screening tests are judged (sensitivity, specificity, predictive values), see screening tests.

Quick revision

• Cachexia: TNF, IL-1, IL-6.
• PTHrP: squamous lung cancer. SIADH, ACTH, Lambert-Eaton: small cell lung cancer.
• EPO: renal cell carcinoma. Trousseau: pancreatic adenocarcinoma.
• AFP liver/yolk sac; β-hCG choriocarcinoma; CEA colon; CA-125 ovary; CA 19-9 pancreas; PSA prostate.
• Cytokeratin epithelial; vimentin mesenchymal; S-100/HMB-45 melanoma; CD45 lymphoma.
• Pakistan: breast (women), oral cavity (men; betel nut, naswar, gutka).

Written by The House Job from standard pathology references (Robbins and Cotran Pathologic Basis of Disease is the book named in the UHS PGET syllabus).

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