Cytological and molecular features of papillary thyroid carcinoma with prominent hobnail features: a case report

Papillary thyroid carcinoma (PTC) with prominent hobnail features is a recently recognized PTC variant. Its histological hallmark is represented by elongated cells showing a high nuclear/cytoplasmic ratio and a hobnail appearance. Few histological studies have been performed showing aggressive clinical and pathological features. Thus, a better patient management might benefit from its early diagnosis on fine needle aspiration (FNA) samples. To date, the FNA cytology of PTC with prominent hobnail features has not been described.

We retrospectively analyzed the FNA taken from a histologically proven PTC with prominent hobnail features. Although there was a certain degree of morphological overlap with the tall cell variant, some peculiar cytological features were observed. In particular, the novel 'comet-like' cell feature could represent the cytological counterpart of the histological hobnailing. V600E BRAF mutation was observed on a matched cytohistological specimen.

Further investigation is required to validate our diagnostic criteria, as the recognition of PTC with prominent hobnail features on FNA may prospectively enable its preoperative diagnosis, suggesting more aggressive neck surgery.