![]() In/out-of-phase: no signal loss on out-of-phase imaging (pheochromocytomas rarely contain a significant amount of intracellular lipid) 12Įnhancement is prolonged, persisting for as long as 50 minutes 4 ~1/3 do not have marked T2 hyperintensity 18Īreas of necrosis/hemorrhage/calcification will alter the signal Some are markedly hyperintense ( lightbulb sign): If necrotic and/or hemorrhagic then the signal will be more heterogeneous Slightly hypointense to the remainder of the adrenal The overall sensitivity is said to be 98% 6. MRI is the most sensitive modality for the identification of pheochromocytomas and is particularly useful in cases of extra-adrenal location. However, studies have shown no evidence to support this theory and nowadays most radiology non-ionic iodinated contrast media guidelines do not place pheochromocytomas as a contraindication to iodinated contrast administration 13,16. It should be noted that suspected cases of pheochromocytomas have been historically managed as a contraindication for iodinated contrast administration, as it could theoretically precipitate a hypertensive crisis. Up to 7% demonstrate areas of calcification 4 Tend to enhance more on the portal venous phase than the arterial phaseġ10-120 HU of enhancement on the arterial phase suggests pheochromocytoma, but is not specific hypervascular metastases could be considered in an appropriate setting There is, however, overlap with some hyperenhancing adenomas May wash out similar to an adrenal adenoma, but they tend to have a greater enhancement in an arterial or portal venous contrast phase. Usually large, heterogeneous masses with areas of necrosis and cystic change This is on account of 98% of tumors being located within the abdomen and 90% limited to the adrenal glands 6. CTĬT is the first imaging modality to be used, with an overall sensitivity of 89%. Pheochromocytomas can have a variable appearance ranging from solid to mixed cystic and solid to cystic 9. Rather, the distinction is made on demonstrating evidence of direct tumor invasion into adjacent organs/structures or the presence of metastases 4. It is also important to note that it is not possible to distinguish malignant from benign pheochromocytomas merely on the direct appearance of the mass. Overall 98% of tumors are in the abdomen, and 90% are confined to the adrenal glands 6. Small extra-adrenal tumors can, however, be a challenge to find. When confined to the adrenal glands, and especially if suspected clinically, the diagnosis is readily made. They can be found along the sympathetic chain as well as in the urinary bladder and organ of Zuckerkandl. Thoracic paragangliomas are rare and only account for 1-2% of all cases of pheochromocytoma.Īs a general rule, tumors in the adrenal region tend to be large at presentation, usually >3 cm, with an average size of approximately 5 cm. They most frequently arise from the chromaffin cells of the adrenal medulla.Īpproximately 10% of all pheochromocytomas are not located in the adrenal glands. Extra-adrenal tumors are more likely to be malignant and metastasize 4. Various pathological scoring systems are in use (PASS, GAPP) to predict differentiation and the likelihood of metastasis 15. This pattern is composed of well-defined clusters of tumor cells containing eosinophilic cytoplasm separated by a fibrovascular stroma. They typically demonstrate a nesting (Zellballen) pattern on microscopy. Pheochromocytomas are a type of paraganglioma. They are catecholamine-secreting tumors derived from chromaffin cells. When results are positive, imaging is then performed to try and localize the tumor or tumors. ![]() The first investigation in cases where pheochromocytoma is suspected is usually 24-hour urinary or plasma metanephrines, metabolites of norepinephrine and epinephrine 19,20. It is a rare but classical cause of uncontrolled secondary hypertension, with a minority having superimposed paroxysmal hypertensive crises 11. Patients may also present with cardiac dysfunction (myocardial infarction, pulmonary edema) or neurological events (severe headache, visual disturbance, hemorrhagic strokes) 5.
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