Distinct Expression of Galectin-3 in Pheochromocytomas

Potential Biomarkers of Metastasizing Paragangliomas and Pheochromocytomas

Paragangliomas and pheochromocytomas (PPGLs) are rare neuroendocrine tumors originating from paraganglionic tissue in many sites of the body. Most PPGLs are characterized by nonaggressive behavior but all of them have the potential to metastasize. PPGLs represent a great diagnostic dilemma as it is difficult to recognize tumors that are likely to be metastasizing; criteria of malignancy can be found both in benign and metastatic forms. This review aims to analyze the current knowledge of the nature of metastasizing PPGLs paying particular attention to head and neck paragangliomas (HNPGLs). Potential predictors of the malignancy risk for PPGLs were summarized and discussed. These data may also help in the development of diagnostic and prognostic strategies, as well as in the identification of novel potential therapeutic targets for patients with PPGLs.

The Expression of Snail, Galectin-3, and IGF1R in the Differential Diagnosis of Benign and Malignant Pheochromocytoma and Paraganglioma

Objective

The aim of this study was to investigate the expression of Snail, galectin-3, and IGF1R in benign and malignant pheochromocytoma and paraganglioma (PPGL) and explore their role in the diagnosis of malignant PPGL.

Methods

We retrospectively collected and analyzed surgical tumor tissue from 226 patients initially diagnosed with PPGL who underwent surgery from Jan. 2009 to Jan. 2016 at West China Hospital, Sichuan University. We observed and quantified the expression of Snail, galectin-3, and IGF1R in paraffin-embedded samples by immunohistochemical staining.

Results

The significant difference in survival time among the three groups (benign PHEO, benign PGL, and potentially malignant PPGL) was compared by Kaplan-Meier survival analysis. The positive staining of Snail, galectin-3, and IGF1R in the benign PHEO group was significantly lower than that in the other three groups (P < 0.001). The Kaplan-Meier survival plots indicated that the survival time of the patients with intense positive staining was significantly lower than that of the patients with weak positive staining.

Conclusion

The intense expression of Snail, galectin-3, and IGF1R may be valuable indicators for the diagnosis of malignant PPGL.

Malignant pheochromocytomas and paragangliomas: a diagnostic challenge

INTRODUCTION

Malignant pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare disorders arising from the adrenal gland, from the glomera along parasympathetic nerves or from paraganglia along the sympathetic trunk. According to the WHO classification, malignancy of PCCs and PGLs is defined by the presence of metastases at non-chromaffin sites distant from that of the primary tumor and not by local invasion. The overall prognosis of metastasized PCCs/PGLs is poor. Surgery offers currently the only change of cure. Preferably, the discrimination between malignant and benign PCCs/PGLs should be made preoperatively.

METHODS

This review summarizes our current knowledge on how benign and malignant tumors can be distinguished.

CONCLUSION

Due to the rarity of malignant PCCs/PGLs and the obvious difficulties in distinguishing benign and malignant PCCs/PGLs, any patient with a PCC/PGL should be treated in a specialized center where a multidisciplinary setting with specialized teams consisting of radiologists, endocrinologist, oncologists, pathologists and surgeons is available. This would also facilitate future studies to address the existing diagnostic and/or therapeutic obstacles.

Expression of galectin-3, nm-23, and cyclooxygenase-2 could potentially discriminate between benign and malignant pheochromocytoma

Currently, the only reliable indicator of malignancy in pheochromocytoma is the presence of distant metastasis or extensive local invasion; predicting behavior of pheochromocytoma remains challenging. We aimed to correlate the behavior of pheochromocytoma with its expression of nm-23, cyclooxygenase (COX)-2, and galectin-3 (genes used to predict the course of some neoplastic diseases), evaluated immunohistochemically in 55 paraffin blocks of formalin-fixed pheochromocytoma specimens with confirmed behavior. In 3 (7%) of 44 benign and 7 (64%) of 11 malignant pheochromocytomas, there was negative nm-23 expression (P = .000). COX-2 immunoreactivity was positive in 10 (23%) of benign and 9 (82%) of malignant tumors (P = .000). Galectin-3 was expressed in 5 (11%) of benign and 9 (82%) of malignant pheochromocytomas (P = .000). Negative nm-23, along with positive COX-2 or galectin-3, predicted malignancy with 100% specificity. Dual negativity for galectin-3 and COX-2, along with nm-23 positivity, indicated benign behavior with 100% sensitivity. In early pheochromocytoma, evaluation of nm-23, galectin-3, and COX-2 expression could predict the outcome. Larger studies seem necessary to confirm the potential practical value of our findings.

Malignant pheochromocytoma: state of the field with future projections

The prevalence of malignant pheochromocytoma is about 10%, and is somewhat higher for paraganglioma. A problem for clinical follow-up is that patients with "benign" histopathologic findings may develop metastatic disease. At the first international symposium on pheochromocytoma in Bethesda (2005) experts from different disciplines and patients shared their experiences, and the present knowledge of this rare disease was updated. The discussion related to future strategies for better clinical/histopathologic diagnosis and understanding of different geno- and phenotypes. Curative surgery can only seldom be performed because of multiple metastases. The main therapeutic goal is therefore often tumor reduction and control of hypertension. To date the best adjunct to surgery is radionuclide therapy using 131I-MIBG, but the background information for optimal treatment is still incomplete. Certain patients may benefit from 131I-MIBG combined with radiotherapy via somatostatin receptors expressed by the tumor, or the combination with chemotherapy. The need for future multicenter studies was emphasized. In experimental models the work on enhanced expression of amine transporters critical for radiotherapy is continued. Ongoing microarray studies will reveal novel intracellular pathways of importance for proliferation/cell cycle control, which can be inhibited by pharmacologic tools.