Paraneoplastic Syndromes: Endocrinologic/Hematologic¶
Chapter 98 | Part 4: Oncology and Hematology
KEY CLINICAL POINTS¶
- Paraneoplastic syndromes arise from tumor-derived substances (hormones, cytokines) causing systemic effects, not directly from mass effect.
- Common endocrinologic syndromes include hypercalcemia (PTHrP), Cushing’s syndrome (ectopic ACTH), and SIADH (vasopressin).
- Hematologic syndromes like erythrocytosis (erythropoietin), thrombocytosis (IL-6), and granulocytosis (G-CSF/GM-CSF) are linked to tumor production of growth factors.
- Diagnosis requires ruling out primary endocrine disorders and confirming tumor hormone production via imaging, immunostaining, or biochemical assays.
- Treatment prioritizes addressing the underlying malignancy, with adjunctive therapies for hormone-related symptoms (e.g., bisphosphonates for hypercalcemia).
1. DEFINITION & OVERVIEW¶
Paraneoplastic syndromes are systemic disorders caused by tumor-derived substances (hormones, cytokines, growth factors) rather than direct tumor invasion or mass effect. These syndromes affect endocrine, hematologic, and other systems. Ectopic hormone production is central to many syndromes, often due to tumor dedifferentiation or genetic rearrangements.
Table 98-1 Paraneoplastic Syndromes Caused by Ectopic Hormone Production¶
| PARANEOPLASTIC SYNDROME | ECTOPIC HORMONE | TYPICAL TUMOR TYPES |
|---|---|---|
| Hypercalcemia of malignancy | Parathyroid hormone–related protein (PTHrP) | Squamous cell (head and neck, lung, skin), breast, genitourinary, gastrointestinal; osteolytic metastases |
| 1,25-Dihydroxyvitamin D | Lymphomas | |
| Parathyroid hormone (PTH) (rare) | Lung, ovary | |
| Prostaglandin E (PGE) (rare) | Renal, lung | |
| Syndrome of inappropriate antidiuretic hormone secretion (SIADH) | Vasopressin | Lung (squamous, small cell), gastrointestinal, genitourinary, breast, ovary |
| Cushing’s syndrome | Adrenocorticotropic hormone (ACTH) | Lung (small cell, bronchial carcinoid, adenocarcinoma, squamous), thymus, pancreatic islet, medullary thyroid carcinoma, pheochromocytoma |
| PARANEOPLASTIC SYNDROME | ECTOPIC HORMONE | TYPICAL TUMOR TYPES |
|---|---|---|
| Corticotropin-releasing hormone (CRH) (rare) | Pancreatic islet, carcinoid, lung, prostate | |
| Ectopic expression of gastric inhibitory peptide (GIP), luteinizing hormone (LH)/human chorionic gonadotropin (hCG), other G protein–coupled receptors (rare) | Macronodular adrenal hyperplasia | |
| Male feminization | hCG | Testis (embryonal, seminomas), germinomas, choriocarcinoma, lung, hepatic, pancreatic islet |
| Diarrhea or intestinal hypermotility | Calcitonin | Lung, colon, breast, medullary thyroid carcinoma |
| Vasoactive intestinal peptide (VIP) | Pancreas, pheochromocytoma, esophagus | |
| Oncogenic osteomalacia | Fibroblast growth factor 23 (FGF23) or phosphatonin | Hemangiopericytomas, osteoblastomas, fibromas, sarcomas, giant cell tumors, prostate, lung |
| Acromegaly | Growth hormone–releasing hormone (GHRH) | Pancreatic islet, bronchial, and other carcinoids |
| Growth hormone (GH) | Lung, pancreatic islet | |
| Hyperthyroidism | Thyroid-stimulating hormone (TSH) | Hydatidiform mole, embryonal tumors, struma ovarii |
| Hypertension | Renin | Juxtaglomerular tumors, kidney, lung, pancreas, ovary |
| Consumptive hypothyroidism | Type 3 deiodinase | Hepatic and other hemangiomas |
| Cancer immunotherapy-associated autoimmune hormone deficiencies | Autoimmune hormone deficiencies | Cancers treated with immunotherapy, particularly anti–CTLA-4, PD-1, PD-L1 |
1.1 Ectopic Hormone Production¶
Tumors may produce hormones from atypical tissues (ectopic) or aberrantly express normal hormones. Examples include ectopic ACTH in small-cell lung cancer (SCLC) and PTHrP in squamous cell carcinomas. Ectopic expression often involves dysregulated feedback mechanisms and peptide processing abnormalities.
1.2 Common Syndromes¶
Key syndromes include hypercalcemia (PTHrP), Cushing’s syndrome (ACTH), SIADH (vasopressin), hypoglycemia (IGF-II), and paraneoplastic endocrinopathies from immunotherapy. Hematologic syndromes include erythrocytosis, thrombocytosis, and granulocytosis.
2. EPIDEMIOLOGY¶
Paraneoplastic syndromes are more common than generally appreciated, often presenting as initial symptoms of malignancy. Hypercalcemia (HHM) occurs in ~20% of cancers, with lung, head and neck, and genitourinary tumors most common. SIADH is linked to SCLC ( ≥ 50% of cases). Hematologic syndromes like thrombocytosis and granulocytosis are seen in 30–40% of solid tumors.
Table 98-2 Paraneoplastic Hematologic Syndromes¶
| SYNDROME | PROTEINS | CANCERS TYPICALLY ASSOCIATED WITH SYNDROME |
|---|---|---|
| Erythrocytosis | Erythropoietin | Renal cancers, hepatocarcinoma, cerebellar hemangioblastomas |
| G-CSF, GM-CSF, IL-6 | ||
| Thrombocytosis | IL-6 | Lung cancer, gastrointestinal cancer, breast cancer, ovarian cancer, lymphoma |
| IL-5 | ||
| Thrombophlebitis | Unknown | Lung cancer, pancreatic cancer, gastrointestinal cancer, breast cancer, genitourinary cancer, ovarian cancer, prostate cancer, lymphoma |
2.1 Risk Factors¶
Risk factors include tumor type (e.g., SCLC, carcinoids), genetic predisposition (e.g., loss of imprinting in IGF-II), and tumor-associated cytokine production (e.g., IL-6, G-CSF).
2.2 Demographics¶
Most common in adults, with lung cancer (SCLC, bronchial carcinoid) and lymphomas being the leading tumor types. Hematologic syndromes are more prevalent in patients with myeloproliferative disorders.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Ectopic hormone production is driven by tumor dedifferentiation, genetic rearrangements (e.g., PTH gene translocation), or dysregulated signaling pathways (e.g., hedgehog, TGF- β ). Epigenetic factors (e.g., hypomethylation of PTHLH) and oncogenic mutations (e.g., Ras, p53) contribute to aberrant hormone expression.
3.1 Molecular Mechanisms¶
Genetic rearrangements (e.g., PTH gene translocation) or epigenetic changes (e.g., hypomethylation) can drive ectopic hormone production. Tumor dedifferentiation leads to expression of fetal or embryonic genes (e.g., IGF-II, hCG).
3.2 Hormonal Pathways¶
Ectopic ACTH (via POMC gene) and PTHrP (via PTHLH gene) activate downstream pathways (e.g., cAMP, MAPK) to induce hypercalcemia, Cushing’s syndrome, or SIADH. IL-6 and G-CSF drive hematologic syndromes.
4. CLINICAL FEATURES¶
Symptoms vary by syndrome: hypercalcemia (fatigue, confusion, renal stones), Cushing’s (central obesity, hypertension), SIADH (hyponatremia, seizures), hypoglycemia (weakness, coma), and thrombocytosis (thrombosis).
4.1 Endocrinologic Syndromes¶
Hypercalcemia: fatigue, polyuria, renal stones. Cushing’s: centripetal obesity, hypertension, purple striae. SIADH: hyponatremia, confusion, seizures. Hypoglycemia: weakness, coma.
4.2 Hematologic Syndromes¶
Erythrocytosis: headache, dizziness. Thrombocytosis: thrombosis, bleeding. Granulocytosis: no symptoms, but increased infection risk.
5. DIFFERENTIAL DIAGNOSIS¶
Differentiate paraneoplastic syndromes from primary endocrine disorders (e.g., hyperparathyroidism, pituitary tumors) and other causes of hyponatremia (e.g., heart failure, renal disease).
5.1 Hypercalcemia¶
Distinguish from primary hyperparathyroidism (normal PTH in HHM) and granulomatous disease (elevated 1,25-dihydroxyvitamin D).
5.2 SIADH¶
Differentiate from heart failure, renal disease, or drug-induced hyponatremia (e.g., thiazide diuretics).
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnostic workup includes serum hormone levels (PTHrP, ACTH, vasopressin), imaging (CT, MRI, PET), and tumor markers (e.g., hCG, calcitonin). Confirm tumor hormone production via immunostaining or mRNA analysis.
Table 98-3 Khorana Risk Score for Venous Thromboembolism in Cancer Patients¶
| PATIENT CHARACTERISTICS | RISK SCORE POINTS |
|---|---|
| Site of cancer | Very high risk (stomach, pancreas): 2; High risk (lung, lymphoma, gynecologic, genitourinary excluding prostate): 1 |
| Prechemotherapy platelet count ‡350,000/mL | 1 |
| Hemoglobin level <10 g/dL or use of red cell growth factors | 1 |
| Prechemotherapy leukocyte count >11,000/mL | 1 |
| BMI ‡35 kg/m2 | 1 |
6.1 Laboratory Tests¶
Measure serum calcium, PTH, PTHrP, ACTH, vasopressin, and electrolytes. Assess renal function and tumor markers (e.g., hCG, calcitonin).
6.2 Imaging¶
CT/MRI for tumor localization; PET/OCT for ectopic hormone sources. Octreotide scans for VIP-secreting tumors.
7. MANAGEMENT & TREATMENT¶
Prioritize tumor-directed therapy (surgery, chemotherapy, radiation). Adjunctive treatments include bisphosphonates for hypercalcemia, glucocorticoids for SIADH, and cytokine inhibitors for hematologic syndromes.
7.1 Hypercalcemia¶
Hydration with saline, bisphosphonates (zoledronate, pamidronate), calcitonin. Treat underlying malignancy.
7.2 SIADH¶
Fluid restriction, vasopressin receptor antagonists (tolvaptan), glucocorticoids. Avoid excessive IV fluids.
7.3 Hematologic Syndromes¶
Anticoagulation for thrombosis; phlebotomy for erythrocytosis. Target tumor with chemotherapy or radiation.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis depends on tumor type and response to therapy. Complications include renal failure, infections, thromboembolism, and adrenal insufficiency. Early diagnosis improves outcomes.
8.1 Complications¶
Hypercalcemia: renal stones, arrhythmias. SIADH: cerebral edema, seizures. Thrombocytosis: thromboembolism. Hypoglycemia: coma, seizures.
8.2 Prognostic Factors¶
Early detection, tumor resectability, and response to therapy. High-risk tumors (e.g., SCLC) have poor prognosis.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Monitor for ectopic hCG production. Pediatrics: Ectopic ACTH in neuroblastoma. Elderly: Increased risk of hypercalcemia and thrombosis. Immunotherapy: Autoimmune endocrinopathies (e.g., hypophysitis).
9.1 Pregnancy¶
Ectopic hCG production in gestational trophoblastic disease. Monitor for hyperthyroidism or hypercalcemia.
9.2 Immunotherapy¶
Autoimmune endocrinopathies (e.g., hypophysitis, thyroiditis) occur in ~10% of patients. Monitor for adrenal insufficiency.
10. KEY POINTS & CLINICAL PEARLS¶
- Paraneoplastic syndromes are systemic effects of tumor-derived substances, not mass effect. 2. Ectopic ACTH (SCLC) and PTHrP (squamous cell cancer) are common causes of Cushing’s and hypercalcemia. 3. SIADH is linked to SCLC and lung tumors. 4. Hematologic syndromes (e.g., thrombocytosis) are driven by cytokines like IL-6. 5. Early diagnosis and tumor-directed therapy are critical for managing these syndromes.