Clinicopathological and molecular features of Napsin A-positive thyroid carcinoma:report of six cases

LUO Bin; HE Huihua; XU Li; HUANG Wenwen; YUAN Jingping

doi:10.3969/j.issn.1007-8096.2025.09.008

Abstract：Objective To investigate the clinicopathological features,immunophenotypic characteristics,molecular alterations,diagnosis,and differential diagnosis of Napsin A-positive thyroid carcinoma(TC).Methods The clinical manifestations,histopathological features,immune/molecular phenotypes and differential diagnosis of Napsin A-positive TC were retrospectively analyzed,and the relevant literature was reviewed and discussed.Results There were 2 females and 4 males,with an average age of 49 years(range,28-67 years).Among them,cervical lymph node puncture biopsy was performed in 3 patients,cervical lymph node excision biopsy was performed in 1 patient,percutaneous lung puncture biopsy was performed in 1 patient,and axillary lymph node puncture biopsy was performed in 1 patient.Histologically,there were 4 cases of micropapillary/hobnail variant of papillary thyroid carcinoma(PTC),1 case of poorly differentiated thyroid carcinoma,and 1 case of classical variant of PTC with micropapillary/hobnail components.Immunohistochemical results showed that PAX-8,Tg,TTF-1,CK7 and CK19 were all positive in 6 patients.Napsin A was positive,with varying staining intensities.Molecular testing revealed TERT promoter mutations.Conclusion The NapsinA-positive metastatic thyroid carcinoma is typically a more aggressive special histological subtype with molecular alterations indicating a poor prognosis.It needs to be differentiated from the NapsinA-positive metastatic lung adenocarcinoma.The positive expression of PAX-8 is critical for the differentiation between the two tumors.