Abstract
INTRODUCTION: Neurofibromatosis type 1 is a hereditary condition often associated with pheochromocytomas but rarely with malignant pheochromocytomas. Neurofibromatosis type 1 is often associated with bone lesions, which complicates the distinction between malignant and benign tumors. CASE PRESENTATION: A 46-year-old man with a medical history of neurofibromatosis type 1 presented with right abdominal pain. Computed tomography revealed a right adrenal tumor, and metaiodobenzylguanidine scintigraphy showed accumulation in the right adrenal gland and thoracic vertebrae. He was diagnosed with pheochromocytoma, and a right adrenalectomy was performed. After surgery, a bone biopsy was conducted on the spinal lesion, confirming metastasis of pheochromocytoma, prompting irradiation. After that, lung and liver metastases emerged, and chemotherapy with cyclophosphamide, vincristine, and dacarbazine was initiated; however, the disease progressed, and he died 11 months after surgery. CONCLUSION: We report a case of malignant pheochromocytoma associated with neurofibromatosis type 1 in which bone metastasis was difficult to diagnose.