Overview of pheochromocytoma
Pheochromocytoma is a tumor of the adrenal gland. Neoplasms composed of chromaffin cells, which tumor cells synthesize and release catecholamines and some may produce peptide hormones. These tumors are the infrequent cause of surgically correctable hypertension. Mutations in genes-RET, NF1, VHL, and three succinate dehydrogenase complex subunit genes, i.e. SDHB, SDHC, and SDHD.
Rule of 10s
- 10% of pheochromocytoma is extra-adrenal-occur in organs of Zuckerkandl and the carotid body.
- The extra-adrenal pheochromocytoma is known as paragangliomas.
- 10% of sporadic adrenal pheochromocytomas are bilateral.
- 10% of adrenal pheochromocytomas metastasize and are malignant (malignancy is more common in extra-adrenal paragangliomas, and tumors developing due to germline mutations).
- 10% not associated with hypertension.
Morphology
Gross:
- Size: Varies and may range from small, circumscribed lesions confined to the adrenal to large hemorrhagic masses.
- Larger tumors masses are well-demarcated & may produce patterns in lobular.
Cut surface:
- Small have yellow-tan.
- Well-defined lesions that compress the adjacent adrenal glands large lesions show areas of hemorrhage, necrosis, and cystic changes.
Chromaffin reaction:
- When the fresh tumor mass tissue is incubated in potassium dichromate solution it turns the tumor become dark brown in color due to oxidation of stored catecholamines. This is termed a positive chromaffin reaction.
Microscopy
- Zellballen pattern
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- The tumor consists of polygonal to spindle-shaped chromaffin cells or chief cells, clustered with the sustentacular cells into small nests or alveoli (Zellballen) separated by a rich vascular network.
- Cytoplasm
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- It has a finely granular appearance due to the presence of granules containing catecholamines.
- Nuclei
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- Round to oval, with a stippled “salt and pepper” chromatin (neuroendocrine tumors).
Electron microscopy
- It shows membrane-bound, electron-dense secretory granules.
Immunohistochemistry
- Neuroendocrine markers include chromogranin and synaptophysin are positive in the case of chief cells.
Criteria for Malignancy
Based on the presence of metastases. Histologic features associated with aggressive behavior and increased risk of metastasis include:
- Numbers of mitoses
- Confluent tumor necrosis
- Spindle cell morphology
- Capsular invasion & vascular invasion may be found in benign lesions of the body.
Clinical features
- Hypertension in 90% of patients.
- Paroxysmal episodes(2/3rd): It is characterized by an abrupt onset, precipitous increases in blood pressure, associated with tachycardia, palpitations, headache, sweating, tremor, and a sense of apprehension.
- Isolated paroxysmal episodes: Less common.
- Chronic sustained increases in blood pressure punctuated by paroxysms.
- The increases in blood pressure are induced by the sudden release of catecholamines.
- This may precipitate congestive heart failure (CHF), pulmonary edema, myocardial infarction (mi), ventricular fibrillation, & cerebrovascular accidents (CVA).
Complications
- Catecholamine cardiomyopathy.
- Catecholamine-induced myocardial instability.
- Ventricular arrhythmias.
Laboratory Diagnosis
- It is based on the demonstration of increased urinary excretion of free catecholamines and their metabolites, such as vanillyl-mandelic acid and metanephrines.
- Isolated benign pheochromocytomas are treated with surgical excision.
- With multifocal lesions, long-term medical (medicinal) treatment for hypertension conditions may be required.
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