No correlation between phaeochromocytoma catecholamine secretion and granule ultrastructure

Background It is uncertain whether biochemical markers of catecholamine sec retion in patients with phaeochromocytoma correlate with tumour ultrastruct ure: granule morphology. Methods Fifteen patients with an adrenal phaeochromocytoma (n = 13) or para ganglioma (n = 2) (three men, 12 women; age 17-79 years) were studied. Cate cholamine secretion was estimated by measuring urinary levels of free norad renaline, adrenaline and dopamine. The number and type of secretory granule s were evaluated by two independent observers on electron micrographs (area analysed approximately 70 mu m(2)). Large round or elongated medium-densit y granules were adrenaline-type granules, whereas electron-dense granules l ying in a vacuole were of noradrenaline type Results No correlation was found between noradrenaline output and the numbe r or percentage of noradrenaline-type granules, although tumours with norma l noradrenaline output had only a minority of this type of granule (less th an 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 varie d significantly (range 7-89 per cent). It was not possible to evaluate the granule type associated with dopamine secretion because one tumour secretin g 14 900 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 s uggests that other factors determine secretory patterns in these tumours.