27. Pulmonary Paraneoplastic syndrome - Cox

• Paraneoplastic syndromes - triggered by an abnormal immune system response to a neoplasm

  • not caused by the direct invasion of cancer cells into tissues but by the production of chemical signals by the tumor
• Pathophysiology of Pulmonary Paraneoplastic Syndromes

  • Endocrine
  • synthesis and release of active substances such as cytokines
  • Immunological
  • cross reaction of antibodies and T cells
  • anti tumor antibodies react with normal tissue
  • cause immune mediated tissue destruction
• Humoral hypercalcemia of malignancy (HHM)

  • mechanism of hypercalcemia are
  • PTHrP (parathyroid hormone related protein)
  • stimulate osteoclastic activity
  • increase poor prognosis of tumor
  • SCC cause bone metastasis
  • increase osteolytic activity
• SIADH is associated with small cell lung cancer
• Trousseau syndrome

  • hypercoagulability causing migratory thrombus
  • cause vessel inflammation
• Trousseau syndrome patho-mechanism

  1. lung adenocarcinoma secrete mucin
  2. mucin interact with platelet selectin causing aggregation
  3. secrete heparinase - degrades endogenous heparin
  4. overexpression of tissue factor - initiate extrinsic coagulation pathway
• Trousseau syndrome - cause thrombosis in superficial vessels
• LEMS - immune mediated like MS

  • impaired presynaptic release of Ach from nerve terminal
  • IgG autoantibody mediated blockage gated Ca2+ channel (VGCC)
• Paraneoplastic neurologic syndrome (PNS)

  • mediated by antibodies and t cells against tumor and normal tissues
  • onconeural antibody
  • autoimmune causing inflammatory degeneration
• Malignant Carcinoid Syndrome - neuroendocrine tumor

  • tumor release vasoactive substances such as serotonin
• Carcinoid syndrome cause

  • right heart sided diseases due to liver metastases
  • tricuspid regurg
  • pulmonary stenosis