Neuroblastoma of the urinary bladder, preclinically detected by mass screening.
BACKGROUND: Since the introduction of mass screening of infants for neuroblastoma, the incidence of neuroblastoma has increased in Japan. The reason for this increased incidence is the possible inclusion of many neuroblastomas that would have regressed spontaneously and would never have been detected clinically. An extremely rare tumor at the dome of the urinary bladder in a 7-month-old infant was detected by the mass screening. METHODS: A case of neuroblastoma of the urinary bladder is reported with a review of the literature. The data in the Japan Children's Cancer Registry are also reviewed to analyze the incidence and the site of origin of neuroblastoma for evaluation of mass screening. RESULTS: A 7-month-old female infant was referred because of a positive urine vanillylmandelic acid screening test. Ultrasonography showed a solid mass attached to the urinary bladder. At laparotomy a 35 x 30 x 25-mm egg-shaped tumor was found at the dome of the bladder, and a partial cystectomy was performed. During the operation no changes in blood pressure occurred when the tumor was manipulated. Histologic diagnosis was rosette-fibrillary neuroblastoma originating in the bladder wall, with a favorable Shimada histopathologic classification. N-myc was not amplified, which predicted a favorable prognosis, and no postoperative chemotherapy was given. The patient was free of symptoms and tumor after a follow-up period of 16 months. Literature review revealed that this was the second case of neuroblastoma of the urinary bladder ever reported in the world, although several cases of pheochromocytoma originating in the bladder wall had been reported. Both neuroblastoma and pheochromocytoma derive from the neural crest. The sympathogonia from the neural crest, a common stem cell, differentiates into a ganglion cell or into a secretory cell known as a chromaffin cell, able to manufacture catecholamines. The first case in the world that was reported as neuroblastoma of the urinary bladder was in a 4-month-old infant who was noted to have a 4-cm lower abdominal mass on routine physical examination. A ganglioneuroblastoma of the dome of the bladder was excised and the patient was doing well. On reviewing the Japan Children's Cancer Registry, the incidence of neuroblastomas in infants has increased as well as the number of stage 1, 2, and 4s (stage 4 special) neuroblastomas since the introduction of mass screening. However, there has been no significant change in the number of stage 3 or 4 diseases diagnosed in older children. According to the Japan Children's Cancer Registry, pelvic origin neuroblastoma, which has been noted to have spontaneous regression, was more frequent in the primary tumors detected by mass screening when compared with those presenting clinically. During preparation of this manuscript another case of bladder dome neuroblastoma was detected by urinary vanillylmandelic acid screening of 6-month-old infants for neuroblastoma in Japan. CONCLUSION: These extremely rare cases of neuroblastoma of the urinary bladder involved children younger than 1 year of age and were incidentally detected by routine physical examination or mass screening. This raises the question of whether these tumors might have regressed spontaneously had they gone undetected and untreated.