[Hobnail variant of papillary thyroid carcinoma]. / Carcinome papillaire de la thyroïde à cellules en clous de tapissier.

ABSTRACT

We report the case of a hobnail variant of papillary thyroid carcinoma revealed by a cervical mass in a 67 years-old patient. This new entity in the 2017 WHO classification is rare. Histopathological diagnosis is based on four main criteria, present in≥30% of tumor cells a discohesive tumor, micropapillary structures and loss of cell polarity and hobnail cells. This tumor expresses markers of thyroid differentiation. The most widely described molecular alteration is BRAF V600E mutation associated with other alterations, especially p53 mutations. This reflects the agressivness of this variant. It is important to recognize the hobnail variant of papillary thyroid carcinoma and to specify it in the pathological report because of its more pejorative prognosis, with local invasion, lymph node and distant metastasis, and deacreased survival. No specific management is recommended, but a close follow up seems necessary.