Abstract: Background：Primary testicular lymphoblastic lymphoma(LBL) in children is rare and mostly secondary, and the previous treatment regimens were mainly chemotherapy combined with local radiotherapy of testis. Modern treatment regimens use high dose methotrexate (HDMTX) and other systematic chemotherapy without testicular radiotherapy. Objective：To summarize the clinical features of pediatric lymphoblastic lymphoma (LBL) with testicular involvement and to investigate the clinical efficacy and prognosis of ALLlike regimen containing HDMTX. Design：Case series report. Methods：The clinical data were collected from 17 pediatric LBL patients with neoplastic lesions and testicular involvement who were treated from January 2009 to April 2017, and chemotherapy was performed with NHL2009LBL regimen (from the modified BFM90 protocol) in lymphoma treatment regimen at Beijing Children's Hospital (BCH) Affiliated to Capital Medical University. The clinical characteristics and the curative effect were analyzed. Main outcome measures：5year overall survival rate(OS) and eventfree survival rate (EFS). Results：Of 277 children with LBL in the same period, 17 were associated with testicular involvement(6.1%), including 5 cases of TLBL and 12 cases of BLBL, with a median age of 6.2(2.613.7) years old. The clinical stages were stage Ⅲ (4 cases) and stage Ⅳ (13 cases). There were 5 cases with mediastinal mass, 3 cases with central nervous system involvement, 12 cases with bone marrow involvement (8 cases of which had reached the leukemia stage), 11 cases of inguinal, pelvic, sciatic/pubic area invasion and 7 cases of giant tumor. Primary testicular lymphoma was found in 1 case and secondary in 16 cases. Bilateral testicular invasion occurred in 6 cases and unilateral testicular invasion in 11 cases. After induction remission treatment, the testicular tumor was evaluated to disappear. The median followup time was 103(3129) months. Among the 17 children, 6 cases relapsed (only 1 case of testicular relapsed who had complete remission after treatment according to the standard protocol and longterm diseasefree survival). Two cases died of recurrence. The 5year OS was (87.5±8.3)%, and the 5year EFS was (68.8±11.6)%. Compared with the overall survival rate of LBL during the same period, the difference was not statistically significant. Conclusions：The clinical symptoms of testicular involvement in pediatric LBL are hidden. Routine Bultrasound examination before chemotherapy can improve the diagnosis rate. The risk of testicular involvement is increased in patients with groin area, pelvis and pelvic invasion. Continued complete remission can be achieved with regular chemotherapy without testicular radiotherapy, and testicular function can be preserved.

Key words: Lymphoblastic lymphoma, Testicular tumor, Children, Antitumor combined chemotherapy regimen