Malignant pheochromocytoma metastasis to the breast shown on I-123 MIBG scan

A 36-year-old woman was referred to our department for I-123 metaiodobenzylguanidine (MIBG)-SPECT/CT scan 3 years after surgical excision of pheochromocytoma. She was referred due to recurrence of her symptoms as well as raised urinary catecholamines. Review of I-123 MIBG scan revealed multiple MIBG-avid metastatic lesions. Most of these were bony lesions, however, there were also 2 soft tissue lesions in the left breast. She subsequently underwent ultrasound-guided fine-needle aspiration of the left breast lesions. Fine-needle aspiration revealed cytologic changes consistent with pheochromocytoma. There has only been 1 previous reported case of pheochromocytoma metastasizing to the breast. This is the first case in which the metastasis was detected by I-123 MIBG scan.