Papillary thyroid carcinoma with nodular fasciitis-like stroma and β-catenin gene mutations: report of a recurrent case.

Papillary thyroid carcinoma with nodular fasciitis-like stroma (PTC-NFS) is a rare lesion with dual pathological features, that behaves more aggressively if positive for β-catenin gene (CTNNB1) mutations. Recently, we encountered a recurrent PTC-NFS with CTNNB1 mutations. A 48-year-old female presented with a recurrent enlarging tumor with a diagnosis of desmoid-type fibromatosis 6 months after her initial operation for PTC-NFS. Over a 2-year observation period, she underwent remedial surgery to resect the recurrent tumor. During the operation, the left recurrent laryngeal nerve was engulfed and scarified. Local invasion, β-catenin aberrant staining, and CTNNB1 mutations were detected both in the primary tumor stroma and the recurrent tumor. This case indicates that CTNNB1 mutation screening and β-catenin staining should be performed in PTC-NFS cases as a predictor for recurrence. If either of these are positive, a wider surgical resection should be adopted to achieve negative margins. Otherwise, radiotherapy should be considered. Furthermore, the lesion might be better known as papillary thyroid carcinoma with desmoid-type fibromatosis in such situations to reflect its local aggressive nature. IJCEP