Endocrine Abstracts

Background: Papillary thyroid carcinoma (PTC), the most common endocrine malignancy, is a tumor of indolent biological and clinical behaviour that usually has a good prognosis. Only a small percentage of patients are affected by aggressive variants of PTC: tall, columnar cell and diffuse sclerosing variants. These aggressive tumor subtypes are characterized by higher rate of local recurrence, regional and distant metastases than classic papillary PTC. Recently another clinically aggressive variant of PTC with hobnail features has been described. However prognostic significance of such focal hobnail component in classic papillary PTC has not been defined.

Cases report: In this study, we reviewed clinical, cytological, histological, immunohistochemical and molecular biological features of five classic papillary PTCs with focal ‘hobnail’ component. Tumors were diagnosed in two woman and three men from 14 to 49 years old (mean age was 31 years). Cytologically these cases were characterized by increased nuclear/cytoplasmic ration of tumor cells, appearance of ‘a shoe nail’, separated arrangement of cells in smears, hyperchromic nucleus, cystic changes (dystrophy and cells degeneration, formation of ‘spherical’ complexes of tumor cells). Prevalence of focal ‘hobnail’ component in histological sections of PTCs was less than 20% of all tumor cells. Tumor size variation ranged from 0.2 to 1.5 cm (mean size was 0.85 cm). Regional metastases of PTC into the neck lymphatic nodes (LN) were diagnosed in all five patients. The BRAF^T1799A point mutation was detected in one of three cases analysed by direct sequencing of DNA extracted from frozen tumor tissue. The size of primary tumor with BRAF^T1799A was 1.5 cm. In four of five patients, the cytological material was obtained preoperatively by FNA from primary thyroid tumor, and metastatic tumors in LN.

Conclusion: PTC with focal hobnail component is characterized by the high frequency of regional metastases at the moment of primary tumor manifestation. Obviously that prevalence of BRAF^T1799A point mutation in PTC with focal hobnail features is similar as in classic papillary PTC without hobnail component.