The histologic distinction between benign and malignant parathyroid tumors is difficult to make. Although cell type is not known to be of prognostic significance, histologic cell types include chief cell, transitional clear cell, and mixed cell types. Standard criteria of malignancy often cannot be confirmed in retrospective reviews of patients with carcinoma. Macroscopic and microscopic infiltrations often do not correlate, and adhesion to surrounding structures does not necessarily imply malignancy. Features such as dense fibrous trabeculae, trabecular growth patterns, mitoses, and capsular invasions, which have been classically associated with carcinomas, have also been found in parathyroid adenomas.[2,3,4] Capsular and vascular invasion appears to correlate best with tumor recurrence.[3,5] In a study of 286 patients, pathologists described well-differentiated carcinomas in approximately 80% of the patients.
An aneuploid DNA pattern is more common, and mean nuclear DNA content is greater in carcinomas than in adenomas; when present in a carcinoma, aneuploidy appears to be associated with a poorer prognosis.[7,8,9] Aneuploidy occurs too frequently in parathyroid adenomas to be significant in differentiating benign from malignant parathyroid lesions.[9,10,11] In general, the clinical course and the gross pathology observed at surgery are as important as the histology to define a lesion as a parathyroid carcinoma.
Schantz A, Castleman B: Parathyroid carcinoma. A study of 70 cases. Cancer 31 (3): 600-5, 1973.
Levin KE, Galante M, Clark OH: Parathyroid carcinoma versus parathyroid adenoma in patients with profound hypercalcemia. Surgery 101 (6): 649-60, 1987.
Bondeson L, Sandelin K, Grimelius L: Histopathological variables and DNA cytometry in parathyroid carcinoma. Am J Surg Pathol 17 (8): 820-9, 1993.
Iacobone M, Lumachi F, Favia G: Up-to-date on parathyroid carcinoma: analysis of an experience of 19 cases. J Surg Oncol 88 (4): 223-8, 2004.
Hundahl SA, Fleming ID, Fremgen AM, et al.: Two hundred eighty-six cases of parathyroid carcinoma treated in the U.S. between 1985-1995: a National Cancer Data Base Report. The American College of Surgeons Commission on Cancer and the American Cancer Society. Cancer 86 (3): 538-44, 1999.