18F-FDOPA PET/CT accurately identifies MEN1-associated pheochromocytoma

SUMMARY

Pheochromocytoma (PHEO) in multiple endocrine neoplasia type 1 (MEN1) is extremely rare. The incidence is reported as less than 2%. We report a case of a 76-year-old male with familial MEN1 who was found to have unilateral PHEO. Although the patient was normotensive and asymptomatic, routine screening imaging with CT demonstrated bilateral adrenal masses. The left adrenal mass grew from 2.5 to 3.9 cm over 4 years with attenuation values of 9 Hounsfield units (HU) pre-contrast and 15 HU post-contrast washout. Laboratory evaluation demonstrated an adrenergic biochemical phenotype. Both 18F-fluorodeoxyglucose (18F-FDG) PET/CT and 123I-metaiodobenzylguanidine (123I-mIBG) scintigraphy demonstrated bilateral adrenal uptake. In contrast, 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET/CT demonstrated unilateral left adrenal uptake (28.7 standardized uptake value (SUV)) and physiologic right adrenal uptake. The patient underwent an uneventful left adrenalectomy with pathology consistent for PHEO. Post-operatively, he had biochemical normalization. A review of the literature suggests that adrenal tumors >2 cm may be at higher risk for pheochromocytoma in patients with MEN1. Despite a lack of symptoms related to catecholamine excess, enlarging adrenal nodules should be biochemically screened for PHEO. 18F-FDOPA PET/CT may be beneficial for localization in these patients.

LEARNING POINTS

18F-FDOPA PET/CT is a beneficial imaging modality for identifying pheochromocytoma in MEN1 patients. Adrenal adenomas should undergo routine biochemical workup for PHEO in MEN1 and can have serious peri-operative complications if not recognized, given that MEN1 patients undergo frequent surgical interventions. MEN1 is implicated in the tumorigenesis of PHEO in this patient.

Adrenal (131)I-6β-iodomethylnorcholesterol scintigraphy in choosing the side for adrenalectomy in bilateral adrenal tumors with subclinical hypercortisolemia

Purpose

Adrenal scintigraphy with 131I-6β-iodomethylnorcholesterol is considered by several authors the gold standard for assessing tumors with subclinical hypercortisolemia. However, most of the described series consist mainly of cases with unilateral lesions. The aim of our study was to assess whether scintigraphy is useful in choosing the adrenalectomy side in the case of bilateral adrenal tumors with subclinical hypercortisolemia.

Methods

The study focused on 15 consecutive patients with benign bilateral adrenal tumors and subclinical hypercortisolemia. The scintigraphy with 131I-6β-iodomethylnorcholesterol was performed. Fourteen patients underwent unilateral adrenalectomy; the gland with predominant uptake on scintigraphy was removed. Cortisol and ACTH concentrations were measured one and six months after surgery. Post-dexamethasone cortisolemia was assessed six months after surgery. To date, the patients have been under postoperative observation for 1–4 years.

Results

Four patients showed unilateral uptake of radiotracer, and nine patients showed predominant accumulation of radiotracer in one of the adrenal glands. The smaller tumor was predominant in 2 cases. Percentage of activity on the predominant side correlates positively with the difference between tumors’ diameters. Unilateral uptake of radiotracer predicts long-lasting postoperative insufficiency of the second adrenal gland. Excision of predominating tumor led to cessation of hypercortisolemia in all patients.

Conclusions

The corticoadrenal scintigraphy is useful in choosing the side for operation in the case of bilateral adrenal tumors with subclinical hypercortisolemia.