OBJECTIVE: To explore the ultrasonographic characteristics of testis tumor in children of different ages.
METHODS: We retrospectively analyzed the clinical data, ultrasonographic results, surgical methods and pathological findings of 76 children with testis tumor treated in Shanghai Children\'s Hospital between April 2013 and March 2018. According to the age at the first diagnosis, we divided the patients into a 0－4 yr (n = 57) and a 5－12 yr group (n = 19), and compared the clinical manifestations, tumor markers, ultrasonographic features such as the tumor size, echogenicity, calcification and color flow images, pathological findings, and surgical methods between the two groups of patients.
RESULTS: Benign tumors were found in 73.4% of the 76 children and in 100% of the patients in the 5－12 yr group, with epidermoid cyst as the most common type (52.6% ［10/19］), 47.4% (9/19) found accidentally, 94.7% (9/19) without elevation of the alpha-fetoprotein (AFP) level, and 94.7% (9/19) treated by testis-sparing surgery (TSS). In the 0－4 yr group, teratoma and yolk sac tumors were the most common and 87.7% (50/57) of the cases were characterized by painless scrotal swelling with a normal or elevated AFP level, treated by TSS or radical orchiectomy. There were statistically significant differences between the two groups of patients in the clinical manifestations, AFP values, pathological findings and surgical methods (all P < 0.05), but not in the ultrasonographic results, mostly solid or mixed cystic-solid masses (χ2 = 0.908, P = 0.635). The maximum diameter of the tumors was smaller and the volume of the healthy contralateral testis was greater in the 5－12 yr than in the 0－4 yr group (t = 2.673 and 2.858, P = 0.009 and 0.010). The proportions of the tumors with calcification and those with grade 0 blood flow were significantly higher in the former than in the latter group (χ2 = 4.825 and 12.298, P = 0.028 and 0.006).
CONCLUSIONS: Testis tumors have different clinical and ultrasonographic features in children of different age groups, malignancy mostly in 0- to 4-year-olds while benignancy commonly in 5- to 12-year-olds, frequently with normal AFP, calcification, and less abundant color blood flow. TSS is recommended for the treatment of testis tumor with serum AFP negative in 5－12 years old children.

Azoospermia is a high risk factor for testicular germ cell tumors, whose underlying molecular mechanisms remain unknown. In a genome-wide association study to identify novel loci associated with human non-obstructive azoospermia (NOA), we uncovered a single nucleotide polymorphism (rs1887102, P=2.60 ×10-7) in a human gene FOXN3. FOXN3 is an evolutionarily conserved gene. We used Drosophila melanogaster as a model system to test whether CHES-1-like, the Drosophila FOXN3 ortholog, is required for male fertility. CHES-1-like knockout flies are viable and fertile, and show no defects in spermatogenesis. However, ectopic expression of CHES-1-like in germ cells significantly reduced male fertility. With CHES-1-like overexpression, spermatogonia fail to differentiate after four rounds of mitotic division, but continue to divide to form tumor like structures. In these testes, expression levels of differentiation factor, Bam, were reduced, but the expression region of Bam was expanded. Further reduced Bam expression in CHES-1-like expressing testes exhibited enhanced tumor-like structure formation. The expression of daughters against dpp (dad), a downstream gene of dpp signaling, was upregulated by CHES-1-like expression in testes. We found that CHES-1-like could directly bind to the dpp promoter. We propose a model that CHES-1-like overexpression in germ cells activates dpp expression, inhibits spermatocyte differentiation, and finally leads to germ cell tumors.