Papillary thyroid carcinoma with desmoid-type fibromatosis or nodular fasciitis-like stroma is an extremely unusual and poorly understood subtype of papillary thyroid cancer. Although prior studies have demonstrated alterations in the Wnt/β-catenin signaling pathway in some of these tumors, controversy still exists regarding the nature of the stromal spindle component. We have studied seven cases of papillary thyroid carcinoma with prominent myofibroblastic stroma, including six men and one woman aged 20-65 years (mean age = 44). All cases displayed areas consistent with conventional papillary thyroid carcinoma embedded in abundant myofibroblastic-like stroma. The myofibroblastic stroma in six cases resembled desmoid-type fibromatosis and in one case it more closely resembled nodular fasciitis. By immunohistochemical staining, the stromal spindle component showed positivity for SMA and low MIB1 proliferation index in all cases, and there was at least patchy strong nuclear positivity for beta-catenin in six/seven cases. Stains for cytokeratin AE1/AE3 and PAX8 were positive in the epithelial elements but negative in the stromal component. Next-generation sequencing was performed on six of seven cases. CTNNB1 gene mutations were identified in six/seven cases. The epithelial component showed BRAF mutations in two cases and an NRAS mutation in one case. The case with fasciitis-like stroma was negative for beta-catenin by sequencing and immunostaining as well as negative for USP6 gene rearrangement. Our findings indicate that papillary thyroid carcinoma with prominent myofibroblastic stroma may represent more than one category of lesions.

• MeSH
• beta Catenin genetics   metabolism   MeSH
• Stromal Cells metabolism   pathology   MeSH
• Adult MeSH
• Immunohistochemistry MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Mutation MeSH
• Myofibroblasts metabolism   pathology   MeSH
• Biomarkers, Tumor metabolism   MeSH
• Thyroid Neoplasms genetics   metabolism   pathology   MeSH
• Thyroid Cancer, Papillary genetics   metabolism   pathology   MeSH
• Proto-Oncogene Proteins B-raf genetics   metabolism   MeSH
• Aged MeSH
• Thyroid Gland metabolism   pathology   MeSH
• PAX8 Transcription Factor genetics   metabolism   MeSH
• High-Throughput Nucleotide Sequencing MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• beta Catenin MeSH
• BRAF protein, human MeSH Browser
• CTNNB1 protein, human MeSH Browser
• Biomarkers, Tumor MeSH
• PAX8 protein, human MeSH Browser
• Proto-Oncogene Proteins B-raf MeSH
• PAX8 Transcription Factor MeSH