Clinical data: a 41-year-old woman was referred for aspiration cytology. She was evaluated of progressive bone pains and repeated nephrolithiasis. Elevated parathormone and serum calcium levels and a nodule in the region of the left thyroid were found.

Palpation: a hard nodule was palpable in the lower pole of the left thyroid.

Laboratory tests: serum-calcium 2.91 mM/L, parathormone 194 ng/mL (normal value: 10-65) and euthyroidism.

Ultrasonography: there was a hypoechogenic lesion dorsal and lateral to the lower pole of the left thyroid. The vascularization was increased.

Preliminary cytology diagnosis: atypical follicular tumor of the thyroid or parathyroid tumor.

Wash-out thyroglobulin level was lower than 0,1 ng/ml.

Serum calcitonin level was in the normal range. Neck and upper mediastinal CT-scan reveled enlarged lymph nodes in the upper part of the mediastinum.

Histopathology : parathyroid carcinoma with metastases to the neck and mediastinal lymph nodes.

Comments:

1. The location of the lesion had to raise the possibility of parathyroid origin.

2. As in most cases of parathyroid tumors the cytological pattern is practically identical with that of a thyroid follicular tumor.

3. Parathyroid carcinoma is a very rare tumor accounting for 0.1% to 5.0% of all cases of primary hyperparathyroidism. It is not only not a cytological diagnosis but even not a preoperative diagnosis.

4. The wash-out technique may be of great help in non-thyroidal lesions.