Metastasis of lung carcinoma in a pheochromocytoma

Tumor-to-tumor metastasis (TTM) is an established but rare entity. Lung carcinoma metastasizes commonly to adrenal glands; however, metastases into an already existing adrenal gland tumor are a rare finding. A 78-year-old man was diagnosed with pheochromocytoma, and during the disease staging, lung involvement was revealed. Functional imaging with both ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ⁶⁸Ga-DOTA-Tyr3-Octreotate (⁶⁸Ga-DOTA-TATE) positron emission tomography (PET) was performed: ¹⁸FDG-PET showed mild uptake in both the adrenal and pulmonary lesions, whereas ⁶⁸Ga-DOTA-TATE-PET revealed intense uptake confined to the adrenal mass. This discordant pattern suggested the presence of 2 biologically distinct lesions. The right adrenal gland was surgically removed, and histology and immunohistochemistry confirmed 2 components within the tumor: a pheochromocytoma that included a lung cancer metastasis. Histopathological confirmation of the pulmonary primary lesion was not available. This is the second published case of a TTM of lung carcinoma inside a pheochromocytoma. Tumor-to-tumor metastasis should be considered in pathological diagnosis.