Urothelial tumors develop from transitional mesodermal cells that line the urinary tract. They are common in adults over the age of 60 and are exceptional in pediatric patients. They are characterized by their low grade, low aggressiveness, and progression [1] [2] . The etiological factors of this uropediatrical pathology are still undetermined, and the therapeutic protocols of various learned societies do not yet take these specific cases into account [3] [4] .

We report the first case of bladder urothelial carcinoma in Gabon in a 12-year-old child. The aim of this study was to present the medical observation of the case and to review the literature on the subject.

A 12-year-old child, A.M.M.A., with no relevant medical history, including schistosomiasis and passive smoking, was seen in consultation in November 2020 for episodes of total and isolated hematuria, of sudden onset without any evidence of trauma, evolving over the past two months.

The physical examination was poor, with a good general condition. Biology revealed a hemoglobin level of 12.2 g/dL, a cytobacteriological examination of the urine without pus or germs, and a urinary search for Schistosoma haematobium eggs, which was negative. Regarding imaging, an ultrasound of the urinary tract was performed, which revealed a unifocal, polypoid, fringed bladder mass on the left lateral wall ( Figure 1 ).

Urothelial tumors are very rare in children [5] . Transitional cell carcinoma of the bladder during the first two decades of life is very rare and poorly characterized. The incidence of tumors is 0.4% in individuals under 20 years of age and 0.03% in those under 16 years of age [5] . Only isolated cases are reported in the literature. The largest pediatric series of bladder tumors is the Surveillance Epidemiology and End Results (SEER) series, which included 140 cases [6] [7] .

The sex ratio in the literature varies from 2:1 to 4:1 [6] . This clear male predominance does not yet have a well-structured rationale.

Risk factors are not well defined, as is the case in adults. Several hypotheses give rise to reflections in the literature: exposure to toxic substances (passive smoking and drug and environmental carcinogens), genetic background, tumor history, history of kidney transplantation, history of chronic infection of the lower urinary tract, and neurological bladders [1] . Bilharzia should not be excluded from these hypotheses because it constitutes the main source of bladder tumors in Africa, with the histological particularity of squamous cell carcinomas [8] .

In our case, the patient was a 12-year-old boy with no history of passive smoking or of living in a schistosomiasis epidemic area.

As in our case, macroscopic hematuria is the primary symptom, with ultrasound confirmation of the bladder mass. Associated signs, often related to the local repercussions of the bladder mass, are abdominal pain and urinary disturbances, which can progress to complete bladder retention [9] [10] .

Diagnostic delay is common and can extend to more than a month due to the unusual nature of bladder tumors in children. A urinary tract infection may be associated. In Hoenig’s series, the circumstances of discovery were macroscopic hematuria in 80% of cases, signs of bladder irritation in 15% of cases, and microscopic hematuria in 5% of cases [11] .

Any discovery of an abnormality on ultrasound should lead to cystoscopy with primary resection of the bladder tumor under general anesthesia for three diagnostic, prognostic, and therapeutic objectives. These are often unifocal lesions. Park reported 94% of single lesions in his series, and Fine reported 100% of unifocal lesions [12] [13] .

The prognosis often depends on the initial histology of the lesion. In children, urothelial tumors are often non-invasive and have an excellent prognosis [1] . Recurrences are rare before the age of 20 and were found in proportions of 0% in the Bujons series, 8% in the Di Carlo series, and 10% in the Fine series [13] - [15] .

From a therapeutic point of view, endoscopic resection of the bladder tumor with anatomopathological examination of the resection chips is essential, and very often constitutes the main part of the treatment [1] .

Some rare cases of high-grade tumors exceptionally require a partial cystectomy of the tumor area as well as complementary treatments: intravesical instillations of BCG, Mitomycin, or MVAC (Methotrexate, Vinblastine, Adriamycin, Cisplatin), based on the adult protocol [13] [16] - [23] .

Thus managed, the surveillance of these children is carried out as in adults.

The histology of the resected tumor in our young patient revealed a low-grade lesion, and he is currently under cystoscopic surveillance, with a normal initial post-tumor resection follow-up.

Urothelial tumors are very rare in children. Any macroscopic hematuria in a child should raise suspicion in the absence of an obvious etiological factor such as trauma, lithiasis, or chronic cystitis. Initial endoscopic resection of the lesion is often the definitive treatment. Often low-grade histologically, their prognosis is good, and the progression is recurrence-free except in cases of high-grade tumors requiring regular monitoring.