Paraneoplastic syndromes

1. Big picture

Paraneoplastic syndromes are symptoms caused by cancer without direct tumor invasion, metastasis, infection, treatment toxicity, or compression. They are clinically important because they may:

1. Appear before the cancer is diagnosed
2. Mimic endocrine, neurological, rheumatological, hematological, or dermatological diseases
3. Indicate an aggressive tumor, recurrence, or occult malignancy
4. Require urgent symptomatic treatment while searching for the underlying cancer

Exam logic:

Unexplained systemic syndrome
+ no local explanation
+ smoker/older age/weight loss/known cancer
= think paraneoplastic syndrome

Classic exam cancers:

• Small cell lung cancer → syndrome of inappropriate antidiuretic hormone secretion, ectopic adrenocorticotropic hormone, Lambert-Eaton myasthenic syndrome
• Squamous cell lung cancer → parathyroid hormone-related peptide hypercalcemia
• Renal cell carcinoma → erythropoietin excess/polycythemia, fever, weight loss, anemia
• Ovarian/breast/small cell lung cancer → paraneoplastic cerebellar degeneration
• Hodgkin lymphoma → pruritus, fever, night sweats, paraneoplastic immune phenomena
• Pancreatic/gastric/lung adenocarcinoma → migratory thrombophlebitis

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