Clinicopathologic Characteristics of Incidentally Identified Pheochromocytoma

Pheochromocytomas are rare neuroendocrine tumors. With the widespread use of cross-sectional imaging, increasing numbers are identified incidentally, but their clinicopathologic traits have been incompletely characterized. We performed a retrospective cohort study of patients who underwent initial adrenalectomy for pheochromocytoma (1997-2014). Patients were classified as identified by guided investigation (GIP) if imaging was performed for symptoms or surveillance and as incidentally identified pheochromocytomas (IIP) if imaging was performed for other indications. Student's t test, Chi square test, or rank-sum tests were used as appropriate. Of 126 patients, 47 % were IIP (n = 59). IIP patients had more nonspecific symptoms, including abdominal or back pain (39.0 vs. 6.0 %, p < 0.001), but lower rates of classic symptoms, such as hypertension (54.2 vs. 77.6 %, p = 0.005), palpitations or arrhythmias (18.9 vs. 50.0 %, p = 0.001), flushing or diaphoresis (25.4 vs. 46.3 %, p = 0.015), and headache (20.3 vs. 44.8 %, p = 0.004). IIP was associated with lower median 24-hour urine metanephrine (2102 vs. 7299 mu g, p = 0.020), normetanephrine (2253 vs. 4383 mu g, p = 0.005), and epinephrine (23 vs. 116 mu g, p = 0.004) levels. Histopathology demonstrated no difference between IIP and GIP in malignant traits, including extraadrenal extension (8.6 vs. 12.3 %, p = 0.568), capsular invasion (26.9 vs. 20.3 %, p = 0.133), lymphovascular invasion (25.0 vs. 24.6 %, p = 0.264), and necrosis (32.4 vs. 20.0 %, p = 0.224). Rates of malignancy were equivalent (5.1 vs. 6.0 %, p = 0.862) between IIP and GIP cohorts. Half of patients presenting for surgical resection of pheochromocytoma were identified incidentally. These patients had equivalent rates of malignancy and pathologic traits associated with malignant potential and require definitive evaluation and early surgical referral.