A 65-year-old female patient was admitted to our hospital presenting with a superior mediastinal big mass that was elastic, hard, and painless. Laboratory data including serum
calcium level and thyroid and parathyroid hormonal functions revealed no abnormalities. Further examination consisting of computed tomography, magnetic resonance imaging, and ultrasonography demonstrated that it was a solid
tumor extending into the superior mediastinum.
Technetium (Tc-99) sestamibi scan revealed a hypofunctioning focus in that area. The preoperative diagnosis was a thyroid
tumor or a metastatic lymph node.
Parathyroid carcinoma was suspected on intraoperative frozen pathological examination. The
tumor was successfully removed with left thyroid lobectomy, and neck node dissection was performed. Macroscopically, it appeared as a dark reddish solid
tumor, and the cut surface presented opalescence. Immunohistology confirmed that there was proliferation of
tumor cells with positive
chromogranin A staining. Thus, the
tumor was diagnosed as
parathyroid carcinoma histopathologically despite a lack of clinical evidence for
hyperparathyroidism. This patient has been followed with no evidence of recurrence, a normal serum
calcium 4 years after surgery, and postoperative
radiotherapy. This report describes a case of nonfunctional
parathyroid carcinoma with a massive mass that
technetium (Tc-99) sestamibi scan failed to detect, and we showed negative immunostaining for
parathyroid hormone (PTH) (N).