Ectopic pheochromocytoma: does the rule of tens apply?

The rule of "tens" is often stated to reflect the distribution and histology of pheochromocytomas, with 10% being bilateral, 10%; ectopic in origin, and 10%; malignant. The objective of this study was to review the ectopic pheochromocytomas in a tertiary endocrine center and to establish whether the rule of tens holds true.

Retrospective data were collected on all adrenalectomies and ectopic pheochromocytoma resections performed between 1993 and 2005 at our institution.

In total, 77 patients had pheochromocytomas: 75%; (58/77) adrenal and 25%; (19/77) ectopic. Of the adrenal pheochromocytomas, 10%; (6/58) were bilateral. The anatomic locations of the ectopic pheochromocytomas were as follows: 26%; (5/19) adjacent to the adrenals, 53%; (10/19) in the organ of Zuckerkandl, 11%; (2/19) in the bladder, 5%; (1/19) in the mediastinum, and 5%;(1/19) in the neck.

Our series demonstrates an incidence of 10%; for bilateral pheochromocytoma, which is similar to that in the published reports. However, 25%; of the pheochromocytomas were ectopic. Zuckerkandl pheochromocytomas were the most common among the ectopic lesions. Rarely, these tumors present outside the abdominal cavity.