Background: Although polyacrylamide hydrogel (PAAG) injection for breast augmentation has been prohibited for many years, the long-term complications will be significant for a long period. Few research articles have focused on the clinicopathological analysis. Materials and Methods: We summarized clinical and pathological features of 90 cases after PAAG-injected breast augmentation, including 2 cases of breast cancer developed following PAAG injection. Results: All patients were females between the ages of 30 and 64 years (mean, 44 years). The complications included masses (75.58%), pain (45.35%), migration (22.09%), deformation (18.60%), infection (16.28%), induration (4.65%), and psychological fear (2.33%). Microscopically, the PAAG presented as purple gel pools, and the foreign body reaction was noted in all 90 patients. The proportion of fibrous component exceeded 90% in 26 cases (28.89%). Chronic and acute inflammation was noted in 70 (77.78%) and 9 (10%) patients, respectively. The mammary gland around the gel displayed atrophy in 18 cases (20.00%), adenosis in 33 cases (36.67%), ductal carcinoma in situ in 1 case (1.11%), and invasive carcinoma in 1 case (1.11%). Conclusion: The long-term complications of PAAG-injected breast augmentation are various and complex. Pathologically, these complications are associated with foreign body reaction, fibrosis, and inflammation. (c) 2019 S. Karger AG, Basel