​A 62-year-old man complaining of neck pain was found to have a mass in the left carotid region. He was on treatment for hypertension but had no symptoms suggestive of catecholamine excess. Urinary dopamine values were near or above the upper reference limit in 2 samples (Table 1). Free and total plasma methoxytyramine, plasma dopamine, and urine methoxytyramine concentrations were above their upper reference limits (46-, 9-, 54-, and 6-fold, respectively). The values for other catecholamines were normal. 

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  1. What is the most likely diagnosis?
  2. What are the clinical signs associated with the production of dopamine and methoxytyramine?
  3. What is the best way to follow this disorder?

Read the article here for the answers.