Development of differential diagnosis for benign and malignant pheochromocytomas

Nuclear imaging to characterize adrenal tumors: Comparison with MRI

AIM: To describe the role of nuclear imaging modalities using nor-cholesterol, metaiodobenzylguanidine (MIBG) and fluorine-deoxy-glucose (FDG) in adrenal tumors for lesion characterization in comparison with magnetic resonance (MR).

METHODS: Population was classified in group 1 consisting of 30 patients with non-hypersecreting unilateral adrenal masses, in group 2 consisting of 34 patients with hypersecreting (n = 19) or non-hypersecreting (n = 15) adrenal adenomas and in group 3 consisting of 18 patients with chromaffin-tissue tumors (CTT), of which 14 were pheochromocytomas while 4 were paragangliomas (n = 4). All patients underwent MR and nuclear studies (nor-cholesterol, MIBG and FDG). Pathology samples (n = 63) or follow-up data in adenomas (n = 19) were used as standard of reference for imaging studies interpretation.

RESULTS: In group 1, MR findings were not highly accurate for lesion characterization, while the results of nuclear scans showed abnormal nor-cholesterol, MIBG and FDG concentration in all cases of adenomas, pheos and malignant tumors, respectively. In group 2, no differences in MR parameters were found between hyperfunctioning and non-hyperfunctioning adenomas, while nor-cholesterol uptake was significantly higher in hyperfunctioning compared to non-hyperfunctioning lesions. In group 3, no differences in MR parameters were found between benign and malignant CCT, while MIBG uptake was significantly higher in malignant compared to benign tumors.

CONCLUSION: On the basis of our findings, nuclear imaging modalities using specific target agents are able to better characterize adrenal tumors, compared with MR. In particular, radionuclide techniques are able to identify the nature of adrenal incidentalomas and to differentiate between hypersecreting and non-hypersecreting adenomas as well as between benign and malignant CTT.

Immunohistochemical markers of the hypoxic response can identify malignancy in phaeochromocytomas and paragangliomas and optimize the detection of tumours with VHL germline mutations

Background:

There are no reliable markers of malignancy in phaeochromocytomas (PCC) and paragangliomas (PGL). We investigated the relevance of the mammalian target of rapamycin (mTOR)/AKT and hypoxic pathways as novel immunohistochemical markers of malignancy.

Methods:

Tissue microarray blocks were constructed with a total of 100 tumours (10 metastatic) and 20 normal adrenomedullary samples. Sections were immunostained for hypoxia-inducible factor 1α (Hif-1α), vascular endothelial growth factor A (VEGF-A), mTOR, carbonic anhydrase IX (CaIX) and AKT. The predictive performance of these markers was studied using univariate, multivariate and receiver operating characteristic analyses.

Results:

In all, 100 consecutive patients, 64% PCC, 29% familial with a median tumour size of 4.7 cm (range 1–14) were included. Univariate analyses showed Hif-1α overexpression, tumour necrosis, size >5 cm, capsular and vascular invasion to be predictors of metastasis. In multivariate analysis, Hif-1α, necrosis and vascular invasion remained as independent predictors of metastasis. Hif-1α was the most discriminatory biomarker for the presence of metastatic diffusion. Strong membranous CaIX expression was seen in von Hippel–Lindau (VHL) PCC as opposed to other subtypes.

Conclusion:

Lack of vascular invasion, tumour necrosis and low Hif-1α expression identify tumours with lower risk of malignancy. We propose membranous CaIX expression as a potential marker for VHL disease in patients presenting with PCC.

Imaging characterization of benign and malignant pheochromocytoma or paraganglioma: comparison between MIBG uptake and MR signal intensity ratio

OBJECTIVE

We compared metaiodobenzylguanidine (MIBG) uptake and magnetic resonance (MR) signal intensity ratio in differentiating benign and malignant disease in patients with pheochromocytoma or paraganglioma.

METHODS

Eighteen patients (9 men, mean age 37 ± 8 years) with pheochromocytoma or paraganglioma underwent MR imaging and iodine-131 MIBG scintigraphy. MR signal intensity ratio was measured on T1 and T2-weighted images using region of interest analysis and intensity ratio of MIBG uptake was calculated for each tumor lesion on 48 h images.

RESULTS

A total of 28 tumor lesions was analyzed of which 12 were benign and 16 malignant. MIBG uptake intensity ratio was significantly higher in malignant lesions compared to benign (5.2 ± 2.4 and 2.9 ± 1.4, respectively, p < 0.01). On the contrary, no significant difference in tumor size and MR signal intensity ratio between malignant and benign tumor lesions was observed.

CONCLUSIONS

In patients with pheochromocytoma or paraganglioma, iodine-131 MIBG uptake is able to differentiate between benign and malignant disease, while MR imaging is not useful for this purpose. The higher MIBG uptake observed in malignant lesions could reflect major tumor storage of catecholamines compared to benign lesions.

Parathyroid hormone-related peptide-producing non-familial pheochromocytoma in a child

We experienced a case of parathyroid hormone-related peptide (PTHrP)-producing pheochromocytoma, which was found in a 12-year-old boy with hypercalcemia. The leading symptom was abdominal pain, and severe hypertension and tachycardia were noticed at the initial visit. His medical and familial histories were unremarkable. Laboratory examinations showed hypercalcemia (3.3 mmol/L of serum-calcium). Computed tomography showed a heterogeneous mass measuring 5.0 cm in the right adrenal gland, which had abnormal uptake with 123-I metaiodobenzylguanidine scintigraphy. Serum/urine catecholamines were highly elevated, and serum PTHrP also increased (1.4 pmol/L). The patient underwent laparoscopic right adrenalectomy. The tumor was histologically diagnosed as typical pheochromocytoma and the expression of PTHrP was confirmed with immunohistochemistry. The serum PTHrP level was normalized after surgery. He was free of disease postoperatively for 12 months. There has been no described pediatric patient with PTHrP-producing pheochromocytoma. We showed evidence that the present tumor is a complex neoplasm involving various neuroendocrine activities with the dual-lineage differentiation.