We describe a case of papillary thyroid carcinoma with fibromatosis/fasciitis-like stroma (PTC-FLS) that contained the rare BRAF c.1799_1801delTGA (p.V600_K601delinsE) mutation, which has not previously been reported in this tumour, as well as the CTNNB1 c.133T>C (p.S45P) mutation.
Twenty-three percent of patients with V600E- and 43% of patients with K601E-mutant melanomas presented with nodal disease at diagnosis compared to just 14% of patients with BRAF wild-type tumors (P = 0.001 and 0.006, respectively).
All cases positive for the BRAF(K601E) mutation were reviewed to confirm histopathologic diagnosis and establish tumor variant, and clinical charts were reviewed to obtain clinical characteristics and follow-up information.
Cytology was consistent with "follicular neoplasia" (negative for galectin-3 immunostaining); molecular analysis on the cytology sample detected a K601E mutation in the exon 15 of the BRAF gene.
This technique, together with an earlier described real-time test specific for V600E and K601E will be useful for research and molecular diagnostic laboratories involved in the study of BRAF-related neoplasia.