A 62-year-old man presented with a 15-year history of paroxysms typical of pheochromocytoma. Previous cardiac and neurological investigations were unremarkable. There had been no intraoperative haemodynamic instability during surgery two years prior.
On examination blood pressure was 141/93mmHg with normal general physical examination and no signs of hormonal excess.
Further testing elucidated elevated plasma normetanephrine 1.45nmol/L (<1.05) and urine noradrenaline 980nmol/24hr (45-680). A CT adrenals did not identify a pheochromocytoma. 68Ga-DOTATATE PET/CT demonstrated avid uptake (SUVmax 23.75g/mL) in the left inguinal region corresponding with a 24x21x24mm nodule in the left inguinal canal with no abnormal uptake elsewhere.
The provisional diagnosis of left inguinal paraganglioma was made. Commencement of pre-operative alpha-blockade with prazosin 2mg three times daily resulted in symptomatic improvement. Beta-blockade with atenolol 25mg daily was commenced pre-operatively after adequate alpha-blockade.
During left inguinal exploration a 25x50cm lesion was identified within the inguinal canal adherent to the spermatic cord, a rare site of genitourinary paraganglioma (1). During manipulation of the lesion the patient became transiently hypertensive to 216/126mmHg with an otherwise unremarkable operative and post-operative course.
Histopathology demonstrated a 30x40x20mm encapsulated nodular lobulated tumour weighing 9g with a solid, hetrogenous yellow and brown surface. Microscopically there was mixed nesting (zellballen) with occasional capsular invasion without tumour extension beyond the fibrous capsule. No vascular invasion was seen and mitotic activity was scant (Ki-67 index <1%). Immunohistochemistry demonstrated positive staining for SDHA and negative staining for SDHB. Negative immunohistochemistry staining for SDHB is strongly associated with a mitochondrial complex II abnormality and can therefore be used to triage formal genetic testing for SDHB, SDHC, or SDHD mutations (2).
Post-operatively his progress has been stable with no further paroxysms and normalisation of his blood pressure off antihypertensives. Both the 24 hour urine noradrenaline level (346nmol/24hr) and plasma normetanephrine (0.37nmol/L) normalised post-operatively.