Abstract
Background: Malignant pheochromocytoma is defined as the occurrence of the tumor in an area that is normally devoid of chromaffin tissue, direct tumor invasion, and/or metastasis. Metastatic malignant pheochromocytoma is very rare. Malignant pheochromocytoma carries a poor prognosis with a 5-year survival rate of 44%. The majority of pheochromocytoma cases are sporadic, but a small portion (10%) can be associated with hereditary syndromes such as neurofibromatosis type 1 (NF1).
Case Report: A 55-year-old Hispanic woman presented to our care with chest pain. Her past medical problems included hypertension, neurofibromatosis type 1 (NF1), and pheochromocytoma status after right laparoscopic adrenalectomy, which was converted to open procedure about 19 months ago. Initial vital signs were significant for tachycardia, tachypnea, and hypertension. Computed tomography (CT) angiography of the chest was performed to rule out a pulmonary embolism, but instead revealed multiple bilateral lung nodules measuring up to 8 mm, consistent with metastasis. CT of the abdomen and pelvis revealed a lytic lesion in the posterior aspect of the left pedicle and transverse process of L4, and the neck/greater trochanter of the left femur. MIBG scan revealed widespread metastatic disease. She received an outpatient chemotherapy regimen of cyclophosphamide, dacarbazine, and vincristine.
Conclusions: Metaiodobenzylguanidine (MIBG) is an alkyl-guanidine derivative similar to noradrenaline, which accumulates in tissue derived from neural crest cells. Current medical literature suggests that therapeutic 131I MIBG has a response rate of 50–75%. Combination chemotherapy using cyclophosphamide, vincristine, and dacarbazine has been the most widely used regimen for malignant pheochromocytoma. This combination of chemotherapy has been shown to have a high response rate and symptomatic improvement. Numerous therapeutic regimens exist for metastatic malignant pheochromocytoma; however, no regimen has been shown to have a benefit significantly superior to the others.

Keywords: Neurofibromatosis 1, Pheochromocytoma, Drug Therapy, Combination