Ectopic pheochromocytoma: does the rule of tens apply?

Introduction: 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.

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

Results: 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.

Conclusions: 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.