Clinical Predictors of Malignancy in Patients with Pheochromocytoma and Paraganglioma

Background and Purpose. Factors associated with malignancy in patients with pheochromocytoma (adrenal tumors, Pheo) and paraganglioma (extra-adrenal, PGL) are not well-defined and all patients require lifelong surveillance. The primary aim of our study was to determine genetic and clinical variables associated with malignancy in patients with Pheo/PGL. Methods. Single institution retrospective review was performed of all patients who underwent surgery (1/95-1/15) for Pheo/PGL. Malignancy was defined as histology-confirmed distant metastasis, lymph nodal involvement, or tumor bed recurrence. Results. A total of 157 Pheo/PGL patients (44 malignant, 113 benign) with mean follow-up of 87 months were included. Compared with patients with benign Pheo/PGL, patients with malignant Pheo/PGL were younger (median 42 vs 50 years, p = 0.014), had larger tumors (median 6.5 vs 4 cm, p < 0.001) and had PGL (63.6 vs 4.4%, p < 0.001). Genetic testing was performed in 60 patients and was positive in 38 (63%). Although positive genetic results were equally likely in malignant vs benign Pheo/PGL (76 vs 54%, p = 0.1), all 11 patients with germline SDHB mutations had malignant disease. In multivariable analysis, younger age, larger tumor size, and PGL were associated with malignancy (p < 0.05). Pheo patients with negative genetic testing and negative family history who developed metachronous metastases all had primary tumors >= 4 cm in size. Conclusions. Patients who are young, have larger tumors, positive genetic testing (especially SDHB) or have PGL require long-term follow-up. Patients with negative genetic testing or family history and Pheo < 4 cm have a lower risk of malignancy, and de-escalated long-term surveillance may be appropriate follow-up.