This study aimed to evaluate immunohistochemical markers of pheochromocytoma/paraganglioma (PPGL) and the relationships between the grading system for adrenal pheochromocytoma and paraganglioma (GAPP) and the prognosis of PPGL in a Chinese population. A retrospective analysis was conducted on a cohort of 102 PPGL cases, from January 2012 to December 2019, with complete clinicopathological and follow-up data. Surgical pathology slides were re-reviewed. All histological parameters involved in GAPP were summarized. The relationship between clinical characteristics, expression of SDHB (succinate dehydrogenase), S-100 and Ki-67 as well as GAPP classifications and prognosis of PPGL was statistically analyzed. The 102 cases included 51 males (50%) and 51 females (50%) with a median age of 48.7 years. The median tumor size was 6.8 cm. Metastases or relapse developed in 23 (22.5%) cases. Larger tumor size, extra-adrenal location, and poorly differentiated PPGL according to GAPP were associated with metastases or relapse (P < 0.05). Histological parameters, including the appearance of large or fused cell nests, necrosis, vascular invasion, and capsular invasion, were more common in the cases with metastases or relapse (P < 0.01). Loss of SDHB or S-100 expression was more common in poorly differentiated PPGL and associated with metastases or relapse (P < 0.01). However, no significant difference in the Ki-67 index between the clinically malignant and benign group was observed. GAPP is thus helpful for evaluations of the biological behavior of PPGL.Copyright © 2022 Elsevier Inc. All rights reserved.