Description

• Pheochromocytoma is an endocrine tumor of chromaffin cells of adrenal medulla.
• These tumors produce epinephrine, norepinephrine, and dopamine; most commonly, norepinephrine (90% of time)
• Tumors are unilateral and mostly benign.

Epidemiology

Incidence
Incidence is 0.8/100,000 person-years.

Prevalence

• Mostly diagnosed in 4th to 5th decade
• It can occur in women and men equally and can affect all ages.
• Average age of diagnosis is 42 years.

Etiology and Pathophysiology

• Pheochromocytomas produce catecholamines in circulation that causes episodic hypertension. Classic triad of symptoms include:
  • Severe headache, sweating, and palpitations
• In 25% of cases, pheochromocytoma cases are familial.
• It is associated with von Hippel-Lindau disease, neurofibromatosis type 1 (NF1), multiple endocrine neoplasia 2.
  • Familial cases tend to recur after surgical resection and occur in more than one sites.

Genetics
Pheochromocytomas are mostly sporadic but can also be familial. Most commonly, familial cases of pheochromocytoma are caused by mutation in succinate dehydrogenase (SDH) subunit gene. Familial pheochromocytomas are all autosomal dominant inheritance. Genes involved in pathogenesis includes:

• NF1 tumor suppressor gene (NH-1)
• RET proto-oncogene mutation
• VHL gene mutation
• TMEM127 tumor suppressor gene mutation
• SDH subunit gene mutations (SDHB, SDHC, SDHD, SDHAF2, SDHA)

Risk Factors

• Adrenal incidentaloma
• Hypertension at young age (<20 years)
• Drug-resistant hypertension
• Unexplained cardiomyopathy and atrial fibrillation

Commonly Associated Conditions

• von Hippel-Lindau disease
• NF1
• Multiple endocrine neoplasia
• Sturge-Weber syndrome
• Tuberous sclerosis
• Renal artery stenosis