A 59-year-old male is found to have a 3.5-cm mass in the right upper lobe of his lung. A biopsy of this mass is diagnosed as a moderately differentiated squamous cell carcinoma. Workup reveals that no bone metastases are present, but laboratory examination reveals that the man’s serum calcium levels are 11.5 mg/dL. This patient’s paraneoplastic syndrome is most likely the result of ectopic production of
Correct Answer: Parathyroid hormone-related peptide
Description: Symptoms not caused by either local or metastatic effects of tumors are called paraneoplastic syndromes. Bronchogenic carcinomas are associated with the development of many different types of paraneoplastic syndromes. These syndromes are usually associated with the secretion of ceain substances by the tumor cells. For example, ectopic secretion of ACTH may produce Cushing's syndrome, while ectopic secretion of antidiuretic hormone (syndrome of inappropriate ADH secretion) may produce hyponatremia. Hypocalcemia may result from the production of calcitonin, while hypercalcemia may result from the production of parathyroid hormone-related peptide (PTHrP), which is a normal substance produced locally by many different types of tissue. PTHrP is distinct from parathyroid hormone (PTH) patients with this type of paraneoplastic syndrome have increased calcium levels and decreased PTH levels. As a result of decreased PTH production, all of the parathyroid glands in these patients are atrophic. Other tumors associated with the production of PTHrP include clear cell carcinomas of the kidney, endometrial adenocarcinomas, and transitional carcinomas of the urinary bladder. Lung cancers are also associated with multiple, migratory venous thromboses. This migratory thrombophlebitis is called Trousseau's sign and is more classically associated with carcinoma of the pancreas. Hyperophic osteoahropathy is a syndrome consisting of periosteal new bone formation with or without digital clubbing and joint effusion. It is most commonly found in association with lung carcinoma, but it also occurs with other types of pulmonary disease. Erythrocytosis is associated with increased erythropoietin levels and some tumors, paicularly renal cell carcinomas, hepatocellular carcinomas, and cerebellar hemangioblastomas. It is not paicularly associated with bronchogenic carcinomas. Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition.
Category:
Pathology
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