Which of the following tumors would most likely be associated with either hyponatremia or diffuse pigmentation of skin?

Small cell carcinomas of the lung can ectopically se­crete antidiuretic hormone (ADH) and adrenocortico­tropic hormone (ACTH) or ACTH-like peptide to produce hyponatremia and Cushing syndrome, re­spectively. Ectopic production of hormones is one of the para­neoplastic syndromes that frequently can predate or accompany cancer. By definition, paraneoplastic syn­dromes must be independent of the direct effect of a rumor or its metastasis. Certain tumors derived from non endocrine cells can ectopically produce hormones, examples of which include the small cell carcinoma of the lung producing ADH or ACTH or a primary squamous cancer of the lung producing a parathor­mone-like peptide. In the process of normal differenti­ation, there is suppression of some genes and activation of others. Carcinogenesis, however, often results in mutations that block the suppressor genes resulting in production of products that are not normally made by those cells. Renal adenocarcinomas have the potential for ec­topically secreting parathormone-like peptide (hyper­calcemia), gonadotropins (feminization or masculini­zation), renin (hypertension), and erythropoietin (secondary polycythemia). Hepatocellular carcinomas can ectopically secrete erythropoietin (secondary polycythemia) and an insu­lin-like peptide (hypoglycemia).