[Cancer developing in the adenoma of the parathyroid gland]

A description of a very rare malignant tumor, cancer of the parathyroid gland which developed in adenoma of this gland is presented. The histological study of the tumor revealed an adenoma of the trabecular structure consisting mostly of dark oxyphilic cells. In its turn, an area of trabecular cancer was found in the adenoma. Complexes of cancer cells infiltrated the adenomal tissue in some sites, but never grew through its capsule. The tumor was hormonally active like most cancers of the parathyroid gland. A particular feature of this case is the development of cancer in adenoma of the parathyroid gland which did not grow beyond the adenoma and produced no metastases.