No correlation between phaeochromocytoma catecholamine secretion and granule ultrastructure

Background It is uncertain whether biochemical markers of catecholamine secretion in patients with phaeochromocytoma correlate with tumour ultrastructure granule morphology. Methods Fifteen patients with an adrenal phaeochromocytoma (n=13) or paraganglioma (n = 2) (three men, 12 women; age 17–79 years) were studied. Catecholamine secretion was estimated by measuring urinary levels of free noradrenaline, adrenaline and dopamine. The number and type of secretory granules were evaluated by two independent observers on electron micrographs (area analysed approximately 70 µm2). Large round or elongated medium-density granules were adrenaline-type granules, whereas electron-dense granules lying in a vacuole were of noradrenaline type. Results No correlation was found between noradrenaline output and the number or percentage of noradrenaline-type granules, although tumours with normal noradrenaline output had only a minority of this type of granule (less than 25 per cent). Adrenaline-type granules were predominant (77 per cent of 163 granules) in a tumour secreting only adrenaline, but the proportion of adrenaline-type granules in six tumours with normal adrenaline output varied significantly (range 7–89 per cent). It was not possible to evaluate the granule type associated with dopamine secretion because one tumour secreting 14900 nmol dopamine and 1570 nmol adrenaline daily had a predominance of noradrenaline-type granules (63 per cent of 132 granules) and two dopamine-secreting tumours (5500 and 4250 nmol per day respectively) had 93 and 13 per cent noradrenaline-type granules. Conclusion The lack of correlation between hormone output and granularity suggests that other factors determine secretory patterns in these tumours.