What is the most common paraneoplastic syndrome?

Hypercalcemia is indeed the most common paraneoplastic syndrome associated with cancer. This condition typically occurs when a tumor secretes parathyroid hormone-related peptide (PTHrP) or other substances that mimic parathyroid hormone, resulting in increased calcium release from bones, enhanced intestinal absorption of calcium, and decreased renal excretion of calcium. This can lead to a variety of symptoms, including fatigue, weakness, confusion, and other systemic effects.

Understanding paraneoplastic syndromes is important because they can often be the first indications of an underlying malignancy, providing critical information for earlier diagnosis and intervention. The occurrence of hypercalcemia, particularly in cancers such as squamous cell lung carcinoma, breast cancer, and renal cell carcinoma, underscores its significance in oncology.