Imaging findings: Ultrasound shows a solid vascularized mass arising from the anterior wall of the bladder to the left side. On CT, this enhances avidly and homogeneously. Other images of the CT study show no associated lymphadenopathy or adrenal masses.
Discussion: The differential diagnosis is as above. Urachal remnant tumour can be discarded, as the lesion is not in the midline. Transitional cell carcinoma of the bladder would be very unusual in a patient of this age. If the patient gave a history of pain in association with menstruation, endometriosis would be a likely explanation. If the history included episodes of fainting during or after micturition (with or without hypertensive crises), a catecholamine-secreting paraganglioma (phaeochromocytoma) should be considered. The lesion was resected; histology showed a non-phaeochromocytoma paraganglioma.
Chromaffin-cell tumours derive from the embryonic neural crest, usually arise from the adrenal medulla, and represent phaeochromocytomas. 10% develop in extra-adrenal sites and are known as paragangliomas. Bladder paragangliomas represent 0.06% of all bladder tumours and 6% of extra-adrenal phaeochromocytomas. They develop from the chromaffin tissue of the sympathetic nervous system in the bladder wall and may be functional or non-functional. They are usually benign, but 15-20% show malignant behaviour.
Functional tumours secrete catecholamines and are associated with hypertensive crises (headaches, palpitations, sweating, flushing) and episodes of hypotension and syncope provoked by micturition, bladder over-distension, sexual activity, defaecation and bladder instrumentation. Seventeen percent of bladder paragangliomas are non-functional and may be asymptomatic or present only with painless haematuria.
US, CT and MRI are useful in tumour localisation; 131I-MIBG (metaiodinebenzylguanidine) nuclear medicine imaging is helpful in detecting catecholamine-secreting primary and metastatic tumours.
Total surgical excision is the usual treatment 
References:  Priyadarshi V, Pal DK, Paraganglioma of urinary bladder. Urology Annals (2015);7(3):402-404
Topic: 11 (Urogenital Radiology)
Subtopic: g (neoplastic disorders (benign and malignant tumors)