Proposal for the histological classification of parathyroid carcinoma.

Although the criteria of Schantz and Castleman are widely used in the diagnosis of parathyroid carcinoma, many tumors diagnosed as carcinoma subsequently do not recur. In addition, although Bondeson's criteria are used to grade parathyroid carcinoma, instances of patient mortality have been documented even in cases where the histological features did not conform to the criteria for high grade. Considering our experience, we believe that the subclassification of parathyroid carcinomas defining tumors limited local infiltration as low-grade and those with widespread infiltration as high-grade may be useful.