Histological types of pediatric renal tumors
As shown in Table 1, a total of 193 patients with renal tumors were diagnosed as WT (123/193, 63.7%) and non-WT (70/193, 36.3%). Based on tumor biology, 95.8% of patients (185/193) presented with malignant tumors, and 4.2% of patients (8/193) with benign tumors. Malignant non-WT was distributed to the following types, CCSK, RTK, CMN, RCC, CPDN, unclassified sarcoma, and primitive neuroectodermal tumor (PNET), with a frequency of (26/185, 14.1%), (9/185, 4.9%), (8/185, 4.3%), (7/185, 3.8%), (6/185, 3.2%), (5/185, 2.7%), and (1/185, 0.5%), respectively. Benign non-WT included cystic nephroma, ossifying renal tumor, metanephric adenoma, hemangioma, and lymphangioma in 4, 1, 1, 1, and 1 patient, respectively.
Age distribution
Age of onset ranged from fetal period to 14 years of age among the 193 patients. There were 8, 34, 39, 35, 21, 17, 16, 7, 4, 2, 3, 2, 1, 3 and 1 patient in each age groups of embryo, 0-≤1 year, 1-≤2 years, 2-≤3 years, 3-≤4 years, 4-≤5 years, 5-≤6 years, 6-≤7 years, 7-≤8 years, 8-≤9 years, 9-≤10 years, 10-≤11 years, 11-≤12 years, 12-≤13 years, and 13-≤14 years, respectively (Figure 1). The 193 patients with renal tumors commonly occurred in early childhood (89/193, 46.2%), followed by infant (73/193, 37.9%), childhood (19/193, 9.8%), embryo (8/193, 4.1%) and adolescent (4/193, 2.0%).
Age distribution and histological subtypes
As shown in Figure 2 and 3, WT (123 patients) were predominantly diagnosed during infant and early childhood, and decreased in proportion with increasing in age, whereas the non-WT (70 patients) variably occurred across different period. CCSK patients occurred from 3 months to 8 years, with a peak incidence rate in 1-≤2 years (9/26, 34.6%). RTK patients commonly occur during infancy and become rare in early childhood. Five out of 8 CMN patients were found in embryo, and the other 3 patients were made diagnostic delay within 1 year of age. RCC patients ranged from 2 to 13 years of age. CPDN patients ranged from 4 to 22 months, and absolutely occurred in infant. Patients with unclassified sarcomas were identified mostly in infant and early childhood.
During the fetal period, CMN, WT and hemangioma were found in 5, 2, and 1 fetus, respectively, from 28 to 38 weeks of gestational age. During early childhood, the most cases presented with WT (68/89), followed by CCSK (10/89), RCC (3/89), sarcoma (3/89), RTK (2/89), cystic nephroma (2/89), and metanephric adenoma (1/89). Non-WT patients occurred more frequently during fetal period (6/70 vs. 2/123, P=0.02), whereas WT was diagnosed more frequently during early childhood (68/123 vs. 21/70, P=0.001).
Clinical features and comparison between WT and non-WT
There were 99 boys and 94 girls among the total patients, with no significant difference between WT and non-WT groups. Among non-WT patients, male gender was predominant in CCSK (M:F=17:9) and CPDN (M:F=5:1), whereas prevalence of female was shown in RCC (M:F=2:5) and RTK (M:F=4:5).
As shown in Table 1, 10.9% of patients were asymptomatic at the time of diagnosis, and that was significantly more common in non-WT patients than WT patients (P=0.04). Abdominal distension was the most common symptom, followed by hematuria, abdominal pain, vomiting, frequent urination and hypertension. Concerned with the location of tumors, left kidney, right kidney, and both kidneys were involved in 95 (95/193, 49.2%), 96 (96/193, 49.7%) and 2 (2/193, 1.1%) patients, respectively. There was no significant difference between WT and non-WT patients.