Cellular Classification of Pheochromocytoma and Paraganglioma
Pheochromocytoma and paraganglioma characteristically form small nests of uniform polygonal chromaffin cells ("zellballen"). A diagnosis of malignancy can only be made by identifying tumor deposits in tissues that do not normally contain chromaffin cells (e.g., lymph nodes, liver, bone, lung, and other distant metastatic sites).
Thymic carcinomas have a greater propensity to capsular invasion and metastases than thymomas. Patients more often present with advanced disease and have a 5-year survival rate of 30% to 50%. Owing to the paucity of cases, optimal management of thymic carcinoma has yet to be defined. As with thymoma, in most published series, carefully selected patients with clearly resectable, well-defined disease, have received complete surgical extirpation. For clinically borderline or frankly unresectable...
Regional or distant metastatic disease is documented on initial pathology in only 3% to 8% of patients; thus, an attempt has been made to identify tumor characteristics associated with future malignant behavior. Pathologic features associated with malignancy include the following:
Large tumor size.
Increased number of mitoses.
Extensive tumor necrosis.
In the absence of clearly documented metastases, no combination of clinical, histopathologic, or biochemical features has been shown to reliably predict the biologic behavior of pheochromocytoma. If no definite malignancy is identified, pathology generally provides insufficient prognostic information regarding the likelihood of recurrence or metastasis. These tumors cannot be considered benign by default; patients require continued lifelong surveillance.[1,2,3,4,5,6,7]
Plouin PF, Chatellier G, Fofol I, et al.: Tumor recurrence and hypertension persistence after successful pheochromocytoma operation. Hypertension 29 (5): 1133-9, 1997.
Thompson LD: Pheochromocytoma of the Adrenal gland Scaled Score (PASS) to separate benign from malignant neoplasms: a clinicopathologic and immunophenotypic study of 100 cases. Am J Surg Pathol 26 (5): 551-66, 2002.
Nativ O, Grant CS, Sheps SG, et al.: The clinical significance of nuclear DNA ploidy pattern in 184 patients with pheochromocytoma. Cancer 69 (11): 2683-7, 1992.
Wu D, Tischler AS, Lloyd RV, et al.: Observer variation in the application of the Pheochromocytoma of the Adrenal Gland Scaled Score. Am J Surg Pathol 33 (4): 599-608, 2009.
Kimura N, Watanabe T, Noshiro T, et al.: Histological grading of adrenal and extra-adrenal pheochromocytomas and relationship to prognosis: a clinicopathological analysis of 116 adrenal pheochromocytomas and 30 extra-adrenal sympathetic paragangliomas including 38 malignant tumors. Endocr Pathol 16 (1): 23-32, 2005.
Linnoila RI, Keiser HR, Steinberg SM, et al.: Histopathology of benign versus malignant sympathoadrenal paragangliomas: clinicopathologic study of 120 cases including unusual histologic features. Hum Pathol 21 (11): 1168-80, 1990.
Tischler AS: Pheochromocytoma and extra-adrenal paraganglioma: updates. Arch Pathol Lab Med 132 (8): 1272-84, 2008.