Paraneoplastic Syndromes

Paraneoplastic Syndromes

Paraneoplastic Syndromes

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Paraneoplastic Syndromes: Overview - Cancer's Sneaky Sidekicks

  • Definition: Remote effects of malignancy; not due to direct tumor mass, invasion, metastasis, or therapy side effects.
  • Prevalence: Affects ~10-15% of cancer patients.
  • Clinical Impact: Earliest sign of occult cancer; mimics metastasis; causes significant morbidity/mortality.
  • **Pathogenesis (Mechanisms):
    • Tumor secretion: Hormones, peptides, enzymes, cytokines (e.g., ACTH, ADH, PTHrP).
    • Immunological: Autoantibodies or T-cells against tumor antigens cross-react with normal tissues.

⭐ Small cell lung cancer (SCLC) is notorious for causing multiple paraneoplastic syndromes, especially SIADH and Cushing's syndrome.

Paraneoplastic syndromes mechanisms: metabolic & immune

Paraneoplastic Syndromes: Endocrine - Hormones Gone Wild

Ectopic hormone production by non-endocrine tumors can cause a variety of syndromes. These often mimic primary endocrine disorders.

SyndromeEctopic Product/MediatorCommon Cancers
Cushing's SyndromeACTHSCLC, Pancreatic, Neural tumors
SIADHADHSCLC, CNS malignancies
HypercalcemiaPTHrP, TGF-$\alpha$, TNF, IL-1Lung (Squamous), Breast, Renal, Ovarian, Multiple Myeloma
HypoglycemiaIGF-2Fibrosarcoma, Other mesenchymal sarcomas, Hepatocellular Ca
Carcinoid Syndrome (metastatic)Serotonin, BradykininBronchial carcinoid, Pancreatic, Gastric
PolycythemiaErythropoietinRenal, Cerebellar hemangioblastoma, Hepatocellular Ca, Leiomyoma

Paraneoplastic Syndromes: Neurological - Brain Under Siege

Neurological paraneoplastic syndromes arise from immune responses against tumors that cross-react with nervous system antigens. Early recognition is key.

SyndromeAssociated Antibody (if any)Common Cancers
Limbic EncephalitisAnti-Hu, Anti-Ma2, Anti-NMDA ReceptorSCLC, Testicular, Ovarian teratoma
Paraneoplastic Cerebellar Degen.Anti-Yo (PCA-1), Anti-Hu, Anti-Tr (DNER)Ovarian, Breast, SCLC, Hodgkin Lymphoma
Lambert-Eaton Myasthenic SyndromeAnti-VGCC (P/Q-type)SCLC (~60%)
Opsoclonus-Myoclonus SyndromeAnti-Ri (ANNA-2) (kids); often noneNeuroblastoma (kids), SCLC, Breast
Stiff-Person SyndromeAnti-GAD, Anti-AmphiphysinBreast, SCLC, Thymoma, Lung
Sensory NeuronopathyAnti-Hu (ANNA-1)SCLC, Neuroblastoma

⭐ Lambert-Eaton Myasthenic Syndrome (LEMS) often presents with proximal muscle weakness that improves with exercise and autonomic dysfunction (e.g., dry mouth); strongly associated with SCLC (Small Cell Lung Cancer).

Paraneoplastic Syndromes: Other Systems - Systemic Shenanigans

  • Hematologic:
    • Polycythemia (↑EPO): Renal cell, hepatocellular ca, hemangioblastoma.
    • Anemia: Chronic disease; Pure Red Cell Aplasia (Thymoma).
    • Trousseau Syndrome (migratory thrombophlebitis): Pancreatic, lung ca.
    • Eosinophilia (Hodgkin lymphoma); Leukemoid reaction.
  • Dermatologic:
    • Acanthosis Nigricans: GI (gastric), lung, uterine ca. Velvety plaques.
    • Dermatomyositis/Polymyositis: Ovarian, lung, breast ca. Gottron's, heliotrope.
    • Leser-Trélat Sign: Sudden seborrheic keratoses; GI adenocarcinomas.
    • Sweet's Syndrome: AML. Painful red plaques.
  • Rheumatologic:
    • Hypertrophic Osteoarthropathy (HOA): Lung ca (NSCLC). Clubbing, periostitis.
    • Palmar Fasciitis & Polyarthritis: Ovarian ca. "Tripe palms". Leser-Trélat sign on neck

⭐ Trousseau syndrome (migratory thrombophlebitis) strongly suggests visceral malignancy, especially pancreatic adenocarcinoma.

Paraneoplastic Syndromes: Diagnosis & Significance - Unmasking the Culprit

  • Diagnosis: High suspicion. Exclude mimics (metastasis, metabolic, infection, drugs). Test specific antibodies (anti-Hu, -Yo). Systematic tumor search.
  • Significance: Often first malignancy sign. Signals recurrence. Severity ≠ tumor burden. Act as tumor markers.

⭐ Lambert-Eaton Myasthenic Syndrome (LEMS) is strongly associated with Small Cell Lung Cancer (SCLC).

High‑Yield Points - ⚡ Biggest Takeaways

  • Eaton-Lambert syndrome (anti-Ca²⁺ channel Abs) is strongly linked to Small Cell Lung Cancer (SCLC).
  • Hypercalcemia (PTHrP-mediated) is common with Squamous Cell Lung Cancer and Renal Cell Carcinoma.
  • SIADH (hyponatremia) & ectopic ACTH (Cushing's) are classic paraneoplastic features of SCLC.
  • Malignant acanthosis nigricans can indicate underlying gastric adenocarcinoma or other visceral cancers.
  • Dermatomyositis/Polymyositis are frequently associated with ovarian, lung, and GI cancers.
  • Polycythemia (ectopic EPO) can occur with Renal Cell Carcinoma, hepatocellular carcinoma, hemangioblastoma.
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Practice Questions: Paraneoplastic Syndromes

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The electrolyte abnormality seen in Ramesh, a 40-year-old patient presenting with polyuria, pain abdomen, nausea, vomiting, and altered sensorium, who was found to have bronchiogenic carcinoma, would be.

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Li-Fraumeni Syndrome is also known as "SBLA" Syndrome, which stands for:S - _____B - Breast CancerL - LeukemiaA - Adrenal Gland tumor

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Li-Fraumeni Syndrome is also known as "SBLA" Syndrome, which stands for:S - _____B - Breast CancerL - LeukemiaA - Adrenal Gland tumor

Sarcoma

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