A rare and easily misdiagnosed tumor of the urinary bladder: Primary composite pheochromocytoma

Background: Composite pheochromocytoma, which is a tumor composed of ordinary pheochromocytoma and other components, is extremely rare in bladder. We present a case of this rarely seen tumor in bladder, and discuss the clinical features, behavior, pathologic findings, essentials of diagnosis and prognosis of this tumor after literature review. Methods: Specimens from a 55-year-old woman with primary composite pheochromocytoma in bladder were analyzed by immunohistochemical (IHC) and fluorescence in situ hybridization (FISH). Clinicopathological characteristics were also collected and discussed. Then, we searched and reviewed literatures related with composite pheochromocytoma that were published in PubMed over the last 80 years. Results: B-mode ultrasound scanner and Magnetic Resonance Imaging (MRI) detected a papillary and infiltrative tumor mass in the irregularly thickened posterior walls of the urinary bladder. Histologically, the tumor showed evidence of big ganglion-liked cells and small round cells in cystoscopy biopsy and typical “Zellballen” structure in gross specimen. On PubMed, a total of 58 cases of composite pheochromocytoma has been reported during 1933-2017. Conclusion: Composite pheochromocytoma in urinary bladder, which has distinctive clincopathologic features, is an extremely rare disease and can only be diagnosed by pathologists. Diagnosis is difficult before histopathological examination and should be considered in patients with no risk factors for usual bladder tumor. The rate of metastasis and death is higher in cases where the second component is not ganglioneuroma. Fortunately, treatment of this type of tumor remains the same as pheochromocytoma. Patients with localized tumors have an extremely favorable prognosis.