Bronchial carcinoma and hypercalcaemia

Hypercalcaemia due to malignant disease, in the absence of bone metastases, is generally regarded as a rare event. It occurred in 16% of a series of cases of bronchial carcinoma coming to necropsy. Hypercalcaemia is a relatively common complication of bronchial carcinoma. The hypercalcaemia is usually accompanied by hypophosphataemia and, in this respect, must be distinguished from the hypercalcaemia that may be found with breast carcinoma. It is frequently accompanied by hypokalaemic alkalosis; this must not be confused with the metabolic disorder that results from the production of ectopic ;ACTH'. The bones sometimes show changes of osteitis fibrosa akin to those seen in hyperparathyroidism. Cystic disease of bone recognizable radiologically is rare, probably because of the relatively short duration of the metabolic disturbance. The parathyroids are usually mildly atrophic. There is no evidence that the main pathogenetic mechanism is stimulation of the parathyroids by the tumour. Acceptable instances of parathyroid hyperplasia are very rare: the significance of these exceptional cases awaits further study.Squamous carcinoma of the bronchus is the type mainly incriminated. Oat-cell carcinoma and bronchial adenocarcinoma are involved less frequently than expected by chance. The significance of the tumour types implicated is discussed in relation to the possible pathogenesis.