Bladder malignant granular cell tumor with EP300 gene mutation: a case report and literature review

Background Malignant granular cell tumor (GCT) is extremely rare. Malignant GCT with EP300 gene mutation in the bladder has not been reported in the literature. Case presentation We report a special case of 45 years old female with malignant GCT of the bladder. Physical examination found a pelvic mass in the patient. Magnetic resonance imaging showed a huge mass between the posterior wall of the bladder, the cervix, and the anterior wall of the vagina. Pathological examination showed that the mass was 11×11×4.5cm in size, involved in the bladder's posterior wall. Under the microscope, the tumor cells were arranged in the shape of a nest or cord to infiltrate the bladder's wall. The tumor cells were pleomorphic, red-stained granular within the cytoplasm, with increased nuclear/cytoplasmic ratio, vacuolar nuclei, and obvious nucleoli. The tumor cells were showed obvious nuclear atypia, and the mitosis was more than 5/50HPF. Coagulative necrosis was widely showed within the tumor. Immunohistochemistry(IHC) showed that S-100, NSE, CD68, CR, α-AT, and TFE-3 were strongly positive, and the Ki-67 proliferation index was around 15%. The next-generation high throughput sequencing indicated that EP300 gene was missense mutated (c.457A>G) with 33% mutation abundance, and genes of DPYD(c.1627A>G),ERCC1( c.354T>C),NQO1(c.559C>T),TPMT(c.719A>G) and XRCC1(c.1196A>G) were polymorphic mutated. The patient died after three months of the second surgical treatment. Conclusions We report for the first time a primary bladder malignant GCM accompanied by mutations in special driving genes such as EP300. We also conducted a comprehensive literature review and an in-depth discussion.