Malignant paraganglioma of the urinary bladder in a 44-year-old female: clinicopathological and immunohistochemical study of a rare entity and literature review.

Paraganglioma of the urinary bladder is a rare pathologic entity with no definitive histological, immunohistochemical or molecular features to determine its malignant potency. Malignancy is essentially determined by the presence of deep local invasion, invasion of adjacent structures, and lymph node or distant metastases. So far, up to 180 cases of paraganglioma have been reported, with less than 30 being malignant. We present a case of malignant paraganglioma of the urinary bladder in a 44-year-old woman. The patient's symptoms were painless hematuria and micturitional headache. The tumor presented the characteristic "zellballen" pattern of growth and immunohistochemically was positive for all neuroendocrine markers. The patient underwent partial cystectomy and the following two postoperative years were uneventful. The literature on paraganglioma of the urinary bladder, analyzing the histological, immunohistochemical and molecular characteristics, is reviewed.