Observer Variation in the Application of the Pheochromocytoma of the Adrenal Gland Scaled Score

Morphologic determination of the malignant potential of adrenal pheochromocytoma is a challenging problem in surgical pathology. A multiparameter Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) was recently developed based on a comprehensive study of a single institutional cohort of 100 cases. Assignment of a PASS was proposed to be useful for identifying pheochromocytomas with potential to metastasize, which defines malignancy according to the current World Health Organization terminology. A PASS is derived by evaluating multiple morphologic parameters to obtain a scaled score based on the summed weighted importance of each. Despite the proposal of this system several years ago, few studies have since examined its robustness and, in particular, the potential for observer variation inherent in the interpretation and assessment of these morphologic criteria. We further examined the utility of PASS by reviewing an independent single institutional cohort of adrenal pheochromocytomas as evaluated by 5 multi-institutional pathologists with at least 10 years experience in endocrine pathology. We found significant interobserver and intraobserver variation in assignment of PASS with variable interpretation of the underlying components. We consequently suggest that PASS requires further refinement and validation. We cannot currently recommend its use for clinical prognostication.