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?: (A) syndrome of inappropriate antidiuretic hormone (SIADH) secretion, (B) acanthosis nigricans, (C) Cushing's syndrome, (D) leukemoid reaction
Answer is A. 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.