Background: Extranodal natural killer/T-cell lymphoma (ENKTL), nasal type, is an aggressive entity within the World Health Organization classification of lymphoid tumors. The International Prognostic Index is reported to be prognostically meaningful for ENKTL, but lacks discriminatory power for stage I/II ENKTL with extensive local invasion. This study aimed to evaluate the prognostic effects of local invasion by site and tissue type in patients with ENKTL. Methods: We retrospectively analyzed data of 86 patients who were diagnosed with ENKTL by the Department of Pathology of Beijing Tongren Hospital from June 2002 to April 2016, and ascertained tumor infiltration of adjacent structures (AS), bone, and soft tissue for each patient, using physical findings and imaging scans. We used univariate and multivariate analysis to assess the association of each involved tissue or site with patients' overall survival (OS). Results: Of the 86 patients, 71(82.6%) experienced invasion of AS, 22(25.6%) of soft tissue, and 26(30.2%) had bone involvement. Overall, patients with AS involvement did not show significantly shorter survival than those without AS involvement (Log rank chi(2) = 1.177, P = 0.278); however, patients who had involved eyeballs or brains showed significantly lower 2-year OS rates than those without eyeball involvement (Log rank chi(2) = 4.105, P = 0.043) or brain involvement (Log rank chi(2) = 7.126, P = 0.008). Patients with involved local soft tissue or bones, respectively, showed lower 2-year OS rates than those without involved local soft tissue (Log rank chi(2) = 10.390, P = 0.001) or bones (Log rank chi(2) = 8.993, P = 0.003). Multivariate analysis showed that involvement of the cheek or facial muscles (hazard ratio, I IR = 5.471, 95% confidence interval [CI]: 1.466-20.416, P = 0.011) and the maxilla bone (HR = 6.120, 95% CI: 1.517-24.694, P = 0.011) were significantly independent predictors of lower 2-year OS rates. Conclusions: Imaging can accurately detect ENKTL invasion of AS, soft tissue, and bone. Involvement of local soft tissue or bone was significantly associated with lower 2-year OS rates. Involvements of the cheek or facial muscle, as well as maxilla bone, are independent predictors of lower 2-year OS rates in ENKTL patients.