ORIGINAL ARTICLESPheochromocytoma of the Adrenal Gland Scaled Score (PASS) to Separate Benign From Malignant Neoplasms A Clinicopathologic and Immunophenotypic Study of 100 CasesThompson, Lester D. R. M.D.Author Information From the Department of Endocrine and Otorhinolaryngic–Head & Neck Pathology, Armed Forces Institute of Pathology, Washington, DC, U.S.A. Presented at the 90th Annual Meeting of the United States and Canadian Academy of Pathology, Atlanta, Georgia, March 5–10, 2001. The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of Defense. Address correspondence and reprint requests to Lester D. R. Thompson, MD, Department of Endocrine and Otorhinolaryngic–Head & Neck Pathology, Building 54, Room G066-11, Armed Forces Institute of Pathology, 6825 16th Street, NW, Washington, DC 20306-6000, U.S.A.; e-mail: [email protected] The American Journal of Surgical Pathology: May 2002 - Volume 26 - Issue 5 - p 551-566 Buy Abstract No comprehensive series has evaluated the histologic features of pheochromocytoma to separate benign from malignant pheochromocytoma by histomorphologic parameters only. Fifty histologically malignant and 50 histologically benign pheochromocytomas of the adrenal gland were retrieved from the files of the Armed Forces Institute of Pathology. The patients included 43 females and 57 males, with an age range of 3–81 years (mean 46.7 years). Patients usually experienced hypertension (n = 79 patients). The mean tumor size was 7.2 cm (weight was 222 g). Histologically, the cases of malignant pheochromocytomas of the adrenal gland more frequently demonstrated invasion (vascular [score = 1], capsular [score = 1], periadrenal adipose tissue [score = 2]), large nests or diffuse growth (score = 2), focal or confluent necrosis (score = 2), high cellularity (score = 2), tumor cell spindling (score = 2), cellular monotony (score = 2), increased mitotic figures (>3/10 high power fields; score = 2), atypical mitotic figures (score = 2), profound nuclear pleomorphism (score = 1), and hyperchromasia (score = 1) than the benign tumors. A Pheochromocytoma of the Adrenal gland Scaled Score (PASS) weighted for these specific histologic features can be used to separate tumors with a potential for a biologically aggressive behavior (PASS ≥4) from tumors that behave in a benign fashion (PASS <4). The pathologic features that are incorporated into the PASS correctly identified tumors with a more aggressive biologic behavior. Application of these criteria to a large cohort of cases will help to elucidate the accuracy of this grading system in clinical practice. © 2002 Lippincott Williams & Wilkins, Inc.