Atypical adenoma of the parathyroid gland. A case report.

Abstract

Background: Atypical parathyroid adenoma is a borderline neoplasm defined by histological findings, while its cytological characteristics have not been described so far.Case: A 43-year-old man was diagnosed as primary hyperparathyroidism due to parathyroid tumor by medical check-up as a momentum. Although the extirpated tumor was welldemarcated by fibrous capsule, a few small tumor nests were observed in the capsule, which fulfilled the histological diagnostic criteria of atypical adenoma. Some of the tumor cells had giant and/or hyperchromatic nuclei, with intranuclear cytoplasmic inclusions in part, which may be used in favor of an estimation of adenoma rather than carcinoma. In addition, there were few mitotic figures in the tumor tissue and Ki-67 labeling index was as low as that in the conventional parathyroid adenomas.Conclusion: It is suggested that the present case is biologically akin to the conventional adenoma and that nuclear atypy and low proliferative activity are useful findings to estimate parathyroid neoplasms to be benign in the cytological specimens.