Endocrine Abstracts

Background: Pheochromocytoma and paraganglioma (PPGL) are rare endocrine tumours that secrete catecholamines. Methoxycatecholamines in free plasma or fractionated methoxycatecholamines in 24-hour urine collections are the recommended tests for the diagnosis of pheochromocytoma, based on which patients are referred for surgical removal of the adrenal gland. However, false-positive results from these tests remain a problem and some patients are referred for adrenalectomy due to suspected pheochromocytoma, but the verifying histopathological examination does not confirm the diagnosis.

Aim: The aim of the study was to assess the characteristics of patients overdiagnosed as pheochromocytoma and undergoing treatment with adrenalectomy.

Methods: Data from 107 adult patients, who underwent laparoscopic adrenalectomy for suspected pheochromocytoma between January 2012 and December 2022, were retrospectively analysed. The patients were divided into two groups: the first, in which the postoperative histopathological examination confirmed the diagnosis of pheochromocytoma (n=74), and the second, in which the suspicion of pheochromocytoma was not confirmed (n=33).

Results: Following histopathological examination of the postoperative material, the diagnosis for 30.8% of the tumours clinically suspected as pheochromocytoma was reclassified. The tumours that were most frequently over-diagnosed as pheochromocytomas were adrenocortical adenomas (n=16) and adrenocortical hyperplasia (n=10). In addition, 3 adrenocortical carcinomas, 1 oncocytic tumour, 1 myelolipoma, 1 metastatic neuroendocrine carcinoma and 1 completely normal adrenal gland were misclassified as pheochromocytoma. Patients with histopathologically confirmed pheochromocytoma were younger (median 56, IQR 23 years vs median 63, IQR 8 years, P=0.027) and had a lower BMI (median 26, IQR 6.4 kg/m² vs median 29.6, IQR 7.6 kg/m², P<0.001). In addition, patients with pheochromocytomas had significantly higher concentrations of metanephrine (median 1119.5, IQR 2868 vs median 175.2, IQR 136 µL/24 h, P<0.0001) and normetanephrine (median 4399.4, IQR 4703 vs median 659.73, IQR 501.9 µL/24 h, P<0.0001) determined in the daily urine collection. There were no statistically significant differences between tumours histopathologically confirmed as pheochromocytoma and false-positive pheochromocytoma with regard to sex, methoxytyramine levels, morning and evening cortisol levels, aldosterone, plasma renin activity, adrenocorticotropic hormone. The size of the adrenal gland on preoperative CT scan and the size of the tumour on histopathology were also not significantly different between groups.

Conclusions: There is still a considerable number of patients undergoing adrenalectomy for suspected pheochromocytoma in whom histopathological verification does not confirm the initial diagnosis. A significant proportion of these are benign tumours that do not need surgical treatment.