Immunohistological study of nonfunctional parathyroid carcinoma. Report of a case

The histological and immunohistological features of a non-functional parathyroid carcinoma obtained from a 56-year-old woman are reported. Macroscopically, the tumor consisted of many small hemorrhagic nodules and showed adhesion to the thyroid gland and esophageal wall. Histologically, the tumor cells resembled parathyroid chief cells, and showed an island-like or sheet-like arrangement, the former showing cystic degeneration and containing hemorrhagic fluid in the extracellular space. Tumor cells resembling water-clear cells and oxyphilic cells were also observed. Most of the tumor cells had glycogen in the cytoplasm. Immunohistologically, the tumor cells showed no staining with anti-thyroglobulin, JT-95 or anti-calcitonin antibodies. However, they were stained with antibodies against chromogranin A (Ch A) and the N-terminal portion of human parathyroid hormone (PTH (N)). The positive staining with anti-PTH (N) antibody disappeared when the antibody was absorbed with excess synthesized human PTH (N). Immunostaining for PTH (N) and Ch A was useful for differentiation of nonfunctional parathyroid carcinoma from thyroid carcinoma and thymoma.