Clinical presentation: A 63-year-old man was referred for an evaluation of a thyroid nodule evolved over more than 5 months. He was treated for cardiac insufficiency.

Palpation: a hard, fixed tumor with uneven surface in the right thyroid bed.

Functional state: euthyroidism with TSH-level 3.49 mIU/L.

Ultrasonography. A large, hypoechogenic mass occupied almost the entire right lobe. The tumor spread substernal.

Cytology resulted in carcinoma corresponding to an anaplastic cancer. Thyroglobulin immunostaining was negative.

Combined clinical-cytological diagnosis: a secondary thyroid carcinoma must be involved in differential diagnostic.

CT examination revealed a tumor in the upper lobe of the right lung.

Perthoracal biopsy of the lung: poorly differentiated squamous cell lung cancer.

Comments.

1. A negative immunocytochemistry is never decisive.

2. All but the time of the evolution of the tumor corresponded to a thyroid anaplastic carcinoma which usually develops within one or two months.