Non-functioning parathyroid carcinoma: a case report

BACKGROUND: Non-functioning parathyroid carcinoma is a rare disease that is difficult to distinguish from other diseases based on the lack of hyperparathyroidism. This is a report of non-functioning parathyroid carcinoma diagnosed by reverse transcription polymerase chain reaction (RT-PCR) targeting parathyroid hormone (PTH) messenger RNA. CASE PRESENTATION: The patient is a 67-year-old male who visited our hospital for the chief complaint of hoarseness. A 5-cm mass was observed in the right lobe of the thyroid gland, and poorly differentiated thyroid carcinoma was suspected according to the fine-needle biopsy results. The laboratory data for thyroid functions, thyroglobulin, anti-thyroglobulin antibodies, calcium, phosphorus, and intact-PTH were all within the normal range. Right recurrent nerve paralysis was observed preoperatively. The patient was diagnosed with poorly differentiated thyroid carcinoma, and total thyroidectomy and central node dissection with partial resection of the right recurrent nerve and esophageal muscle were performed. The pathological findings revealed atypical cells containing clear cells in solid and alveolar structures with broad fibrosis. Mitosis, focal coagulative necrosis, and vascular and capsular invasions were observed. A slightly positive PTH immunohistochemical stain was noted, whereas the RT-PCR results were positive. We finally diagnosed this tumor as non-functioning PTC. No distant metastasis occurred, and the patient is still alive. CONCLUSIONS: This is a report of a patient with non-functioning parathyroid carcinoma, which is clinically very rare. We diagnosed this tumor as non-functioning parathyroid carcinoma using RT-PCR for PTH mRNA.