Background and aims
Malignant transformation of pheochromocytomas/paragangliomas (PCC/PGL) is a rare occurrence, and predictive factors for the same are not well understood. This study aims to identify the predictors of malignancy in patients with PCC/PGL.
Materials and methods
We performed a retrospective analysis of 142 patients with either PCC or PGL registered at our institute between 2000 and 2015. Records were evaluated for clinical parameters like age, gender, familial/syndromic presentation, symptomatic presentation, biochemistry, size, number and location of tumours and presence of metastases and mode of its diagnosis.
Twenty patients were found to have metastases; 13 had metastases at diagnosis and seven during follow-up. Metastases were detected by radiology (CT-neck to pelvis) in 11/20 patients (5/13 synchronous and 6/7 metachronous), 131I-metaiodobenzylguanidine in five (2/12 synchronous and 3/6 metachronous) patients and 18F-flurodeoxyglucose PET/CT in 15 (12/12 synchronous and 3/3 metachronous) patients. Malignant tumours were significantly larger than benign tumours (8.3 ± 4.1 cm, range: 3–22 cm vs 5.7 ± 2.3 cm, range: 2–14 cm, P = 0.0001) and less frequently metanephrine secreting. On linear regression analysis, tumour size and lack of metanephrine secretion were the independent predictors of malignancy.
Patients with primary tumour size >5.7 cm and lack of metanephrine secretory status should be evaluated for possible malignancy not only at diagnosis but also in the postoperative period. As compared to CT and 131I-MIBG scan, 18F-flurodeoxyglucose PET/CT analyses are better (sensitivity: 100%) for the diagnosis of metastases in our study.