Limitations of functional imaging in a patient with phaeochromocytoma
Amin A, Win Z, Palazzo FF, Meeran K, Martin NM, Hatfield E
Imperial Centre for Endocrinology
We present a case of a 20 year old Psychology student who presented with a two year history of sweating. His blood pressure had been high at 150/100 at his surgery. He had recently reported abdominal pain, which prompted his general practitioner to request an ultrasound scan of his abdomen. The ultrasound revealed a right sided suprarenal mass of 4.9x3.4x4.2cm. He was subsequently referred to endocrinology for further management. A CT scan of his abdomen confirmed a 4.6 cm right sided adrenal lesion. Two sets of 24 hours urinary catecholamines showed markedly elevated levels of noradrenaline of 24.47 and 24.82 umol (NR 0.00-0.50) and a mildly elevated dopamine of 3.87 and 3.69 umol (NR 0.00-2.70). Plasma noradrenaline was found to be markedly elevated at 80.9 nmol/l (NR 0.00-0.50). MIBG scintigraphy was performed; however there was no increased MIBG uptake in the lesion. A Gallium-68 DOTATATE scan was subsequently performed which confirmed a moderate sized adrenal lesion with a necrotic centre. He was commenced initially on phenoxybenzamine alone, with subsequent addition of atenolol. The patient underwent a laparoscopic adrenalectomy, the histology of which is awaited.
This case, in line with two others within our trust, highlights the limitations of MIBG scintigraphy. Due to similarities between MIBG and noradrenaline, it has been commonly used in the diagnostic pathway of phaeochromocytoma for over 20 years. However, MIBG scintigraphy has been shown to have reduced sensitivity in some familial paraganglioma syndromes, malignant disease and extra-adrenal paragangliomas. (123)I-MIBG has a reported specificity of 99% and sensitivity of 90%. Other data suggest that 123I-MIBG scintigraphy is negative in 15% of cases of benign phaeochromocytoma and 50% of cases of malignant phaeochromocytoma. Until recently, (18)F-fluoro-deoxy-D-glucose ((18)F-FDG) has been commonly used in the assessment of neuroendocrine tumours. Gallium-68 is a promising new PET tracer which may be superior to 18-F-FDG, due to its short half-life and flexible labelling ability to a wide range of peptides and antibodies.