Parathyroid carcinomas are rare and usually difficult to diagnose, both clinically and histologically.

A 60-year-old man was hospitalised for hypotension. Investigations revealed renal failure associated with hypercalcaemia and elevated serum parathormone. ^99mTc-sestamibi scintigraphy of the parathyroid glands (PT) revealed a mass in the right PT that was treated by parathyroidectomy and recurrent laryngeal lymph node dissection. Histological examination demonstrated a tumour with numerous cytonuclear atypias and immuno-histochemistry demonstrated PTH expression by tumour cells without loss of parafibromin expression. The diagnosis of PTC was based on criteria of invasion and local aggressiveness, despite the absence of lymph node metastasis. The patient developed four recurrences, treated surgically and by adjuvant radiotherapy.

The diagnosis of PTC is usually difficult to establish on a simple histological examination in the absence of specific cytological, architectural or immuno-histochemical markers. This diagnosis must therefore be based on a combination of clinical, radiological and histological signs in a context of atypical presentation of parathyroid tumour.