Bladder cancer associated with schistosomiasis has frequently been reported in Schistosoma endemic regions of the world especially in African countries [7, 8]. This Schistosoma-associated cancer has peculiar features: younger age, advanced-stage at diagnosis and squamous cell type histology [1, 7]. In contrast in Western countries and in non-endemic areas, the mean age of patients with bladder cancer is higher and urothelial carcinoma is the most frequent histological type (more than 90%) [7, 14, 15]. Our current cases typically illustrate these particular features of Schistosoma-associated cancer (younger patients of 37 and 38 years, with advanced-stage squamous cell carcinoma). Cases of bladder squamous cell carcinoma have been reported in Western and industrialised countries and they differ from those found in Schistosoma-endemic areas [16]. Patients are older (mean age ranging around 65 to 68 years) but with advanced-stage cancer like in Schistosoma-endemic areas [14, 15, 17,18,19]. Table 1 summarises the differential characteristics between the main urinary bladder carcinomas.

The causative role of Schistosoma heamatobium is largely admitted and frequently proven by epidemiological studies that usually show associated parasites eggs within the tumor [7, 8]. What is still debated is the mechanism underlying the pathophysiology of bladder cancer associated with schistosomiasis [5]. Histologically a stereotypic sequence of changes is observed in animal models and in human patients: bladder urothelial hyperplasia, squamous cell metaplasia, squamous cell in situ carcinoma and invasive squamous cell carcinoma [1, 5]. In fact, our case 2 patient had metaplastic squamous epithelium around the invasive tumor, supporting the above-mentionned histological sequence of changes associated with schistosomiasis. The WHO (World Health Organisation) considers Schistosoma heamatobium as Group 1 carcinogen to humans (Group 1, corresponding to suspected carcinogens with the strongest evidence) [5]. The mechanisms of bladder malignant transformation by Schistosoma heamatobium is mainly thought to be indirect rather than direct. The eggs deposition by adult worms in tissues induces intense chronic inflammatory reaction with subsequent release of growth factors and other biochemical substances with carcinogenic effects [5, 9, 20]. Also, this chronic inflammation alter the host local immune system leading to co-infections by bacterial and viral agents that promote malignant transformation of the bladder epithelium. Our 2 cases were HIV negative, but they lived in endemic schistosomiasis areas (Niger River Valley) and they were not cigarettes smokers, so we cannot speculate about the role played by other factors in the occurrence of their bladder cancers.

All of these mechanisms act in conjunction with environmental factors (tobacco, diet, industrial products) to induce rapid progression toward invasive squamous cell bladder carcinoma [1, 5].

The prognosis of advanced stage bladder cancer is dismal and the only efficient measure is the eradication of Schistosomal parasites with all their chain of transmission by treating exposed population by praziquantel and providing them with clean water [1, 7, 17]. These policies have been implemented with success in certain countries like Egypt with a significant epidemiological outcome [7]. Unfortunately many African countries are still behind in implementing adequate measures to control schistosomiasis and will continue to register devastating complications of this diasease (bladder cancer) as illustrated by our current reported cases.