A 74-year-old man with a history of smoking notices blood in his chronic daily sputum production. He has no fever or chills, but has lost 10 lb in the past 6 months. On examination, he has bilateral expiratory wheezes, and his fingers are clubbed. There are no lymph nodes and the remaining examination is normal. CXR reveals a left hilar mass. Which of the following suggests that the tumor is a small cell lung cancer?

Paraneoplastic syndromes are classified as metabolic, neuromuscular, connective tissue, dermatologic, and vascular. Stevens-Johnson syndrome usually follows drug allergy. Acanthosis nigricans and other cutaneous manifestations (e.g., dermatomyositis) are rare (<1%). Clubbing is common and occurs in up to 30% of non-small cell lung cancers. The various endocrine syndromes occur in 12% of cases. At times, paraneoplastic syndromes may be the presenting finding in lung cancer or be the first sign of recurrence. Most occur with non-small cell lung cancer, but SIADH is more characteristic of small cell lung cancer.