Endocrine Abstracts

Case history: We present a 71 year old man, with a 3 year history of problematic hypertension (BP exceeding 190/100 on treatment), incidentally found to be hypokalaemic (K 1.8 mmol/l) during investigations for leg weakness. He had no clinical features to suggest an endocrinopathy. Investigations at his local centre revealed hypokalaemia dating back over 3 years.

Investigations: Biochemistry:

Na 142 mmol/l (135–145 mmol/l)

K 1.8 mmol/l (3.5–5.5)

Plasma metadrenaline <180 pmol/l (<1000 pmol/l)

Plasma normetadrenaline <270 pmol/L (<600 pmol/L)

24 h UFC 81 nmol/24 h (<146 nmol/24 h)

Cortisol day profile: normal diurnal rhythm

Aldosterone <70 pmol/l (90–405 pmol/l)

Renin 6 mU/l (5.4–60 mU/l)

11-deoxycortisol 20 nmol/l (7–13 nmol/l).

Urinary steroid profile: An ACC is indicated by high concentrations of metabolites of 11-deoxycortisol, tetrahydro-11-deoxycortisol (456 ug/l) and 11-deoxycorticosterone, tetrahydrocortocosterone (93 ug/l).

Imaging: Triple-phase adrenal protocol CT: 6.5 cm right adrenal mass with unenhanced attenuation of 25 HU and enhancement washout of 57%. Metomidate PET-CT: 67 × 44 mm mass with heterogeneous uptake (TOF SUVmax 31.4) (Sharp IR SUVmax 41.5). Areas of low attenuation and photon deficiency are seen within this mass suggesting necrosis. ¹⁸FDG PET-CT: 65 mm right adrenal mass with heterogeneous tracer uptake with a focus of high peripheral uptake (corresponding to the photon-deficient area on Metomidate PET-CT). (SUVmax=7.3). No evidence of disseminated disease.

Histology: Immunohistochemistry shows tumour cells positive for adrenal cortical markers and negative for chromogranin. The proliferation index in the solid area corresponding to the area of high FDG uptake, is up to 15%, with a background proliferation index of 3%. This favours an oncocytic adrenocortical tumour with a solid area of malignant transformation in keeping with oncocytic adrenocortical carcinoma. No histological features of necrosis were seen to explain the photopenic region on metomidate PET-CT.

Results and treatment: The patient underwent a laparoscopic adrenalectomy. Five months post operation, there is no radiological or biochemical evidence of disease recurrence.

Conclusions and discussion: We present a case of a rare 11-deoxycortisol secreting oncocytic adrenocortical carcinoma with features suggestive of adenoma-carcinoma progression in a patient with a 3 year history of hypertension and hypokalaemia. This case demonstrates the clinical utility of molecular imaging in adrenal tumours, as two distinct areas on CT were seen, which had reciprocal avidity for metomidate and FDG PET and correlated with a discrete nodule with malignant transformation within a larger oncocytic neoplasm on histological review.