Endocrine Abstracts

Introduction: Pheochromocytomas are tumors derived from the adrenal-medullary chromaffin cells that normally produce catecholamines. Rarely these tumors are non-secreting. In the assessment of a suspected pheochromocytoma, guidelines recommend dosing urinary or plasma metanephrines.

Objective: To evaluate the prevalence of pheochromocytomas biochemically non-secreting and their differences.

Methods: We searched all patients with measurements of metanephrines made in an endocrinology department since 1999 (when Clinical Pathology was computerized). We included all those who had performed adrenalectomy in this institution with pheochromocytoma histology. Urinary metanephrines were measured with spectrophotometric chromatographic method (Pisano).

Results: We analyzed 2336 results of urinary metanephrines. 190 were excluded because it was results from outside patients and therefore could not be correlated clinically. The 2146 results corresponded to 1211 patients, with 37 pheochromocytomas analyzed. 13 cases of pheochromocytoma were excluded due to measurements of metanephrines only after surgery. Of the 24 patients, eight had normal values. Of these, three had positive values after analytical revaluation, (two with tumor <1 cm and 1 with ≥3 cm), one had positive values at diagnosis, with a normal value under methyltyrosine and phenoxybenzamine, four patients always had negative values: two with SDHB mutation (tumors >3 cm), one with SDHC mutation (12 cm) and the other with MEN2a (1.5 cm).

All patients had negative assay results also negative vanil-lmandelic acid.

Conclusion: The authors argue that pheochromocytomas may have normal values when they have diameters <1.5 cm or when they have mutations that might interfere with the production of catecholamines (ex: SDHB). Our study reveals the need for repeated measurements of metanephrines, to exclude pheochromocytoma, in the presence of an adrenal tumor in imaging, when the initial measurement is negative.