Ref: Robbins Pathologic Basis of Disease, 8th edition, Pg: 677Explanation:"Paraneoplastic syndromes are common in patients with lung cancer, especially those with SCLC. and may be the presenting finding or the first sign of recurrence " (Ref: Harrison)"'Any one of the histologic types of tumors may occasionally produce any one of the hormones, but tumors that produce ACTH and ADH are predominantly small cell carcinomas, whereas those that produce hypercalcemia are mostly squamous cell tumors <& Small cell lung cancer type is most commonly associated with ectopic hormone production. " (Ref: Robbins)Paraneoplastic syndromes: Symptom complexes in cancer-bearing individuals that cannot readily be explained, either by the local or distant spread of the tumor or by the elaboration of hormones indigenous to the tissue from which the tumor arose. Paraneoplastic Syndromes associated with lung carcinomasLung carcinoma can be associated with several paraneoplastic syndromes . some of which may- antedate the development of a detectable pulmonary lesion.The hormones or hormone-like factors elaborated include:Small cell CaAntidiuretic hormone (ADH), inducing hyponatremia due to inappropriate ADH secretionSmall cell CaA drenocorticotropic hormone (ACTH). producing Cushing syndromeSqamous cell CaParathormone, parathyroid hormone-related peptide, prostaglandin E. and some cytokines, ail implicated in the hypercalcemia Calcitonin, causing hypocalcemia Gonadotropins, causing gynecomastiaLung carcinoid syndromeSerotonin and bradykininThe incidence - 1% to 10% of all lung cancer patients.Tumors that produce ACTH and ADH are predominantly small cell carcinomas. whereas those that produce hypercalcemia are mostly squamous cell tumors.Lambert-Eaton myasthenic syndrome, in w hich muscle weakness is caused by auto-antibodies (possibly elicited by tumor ionic channels) directed to the neuronal calcium channel peripheral neuropathy, usually purely sensory; dermatologic abnormalities, including acanthosis nigricans: hematologic abnormalities, such as leukemoid reactions; and abnormality of connective tissue called hypertrophic pulmonary osteoarthropathy, associated with clubbing of the fingers.Apical lung cancers in the superior pulmonary sulcus tend to invade the neural structures around the trachea, including the cervical sympathetic plexus, and produce a group of clinical findings that includes severe pain in the distribution of the ulnar nerve and Horner syndrome (enophthalmos. ptosis, miosis, and anhidrosis) on the same side as the lesion. Such tumors are also referred to as Pancoast tumors.Paraneoplastic Syndromes(See table in the next question)