Cytological, histological and immunohistochemical characteristics of the macrofollicular variant of thyroid papillary carcinoma

Aim: The macrofollicular variant of papillary thyroid carcinoma (MFV-PTC) is a rare entity which can be confused easily with adenomatous nodules (AN) due to their macrofollicular architecture and bland cytologic features. In this study, we aimed to exhibit detailed cytopathological and immunohistochemical features of MFV-PTC and obtain -if ever exists- new clues with fine needle aspiration (FNA) cytology and immunohistochemistry, especially with nuclear factor kappa B (NF-κB) for differential diagnosis. Materials and methods: After reviewing forty cases of MFV-PTC, 20 cases of PTC (10 follicular variant/FV-PTC, 10 classical varyant/CV-PTC) and 20 cases of AN and their 43 FNAs histologically and cytologically, all cases were assessed in terms of cytokeratin-19 (CK-19), Hector Battifora mesothelial-1 (HBME-1), galectin-3 (Gal-3) and NF-κB immunostaining scores. All findings in related groups were compared statistically with each other. Results: Comparement of nuclear enlargement, nuclear overlapping and chromatin coarsening in FNA biopsies were found to be statistically different between MFV-PTC and PTC and between malignant lesions and AN (p≤0.05), while no relationship between MFV-PTC and AN was found with respect to these findings. The other evaluated cytological parameters were not seem to be useful in differentiating the groups. As for immunohistochemical studies, statistically significant differences were found between MFV-PTC/CV-PTC, MFV-PTC/AN groups and malignant lesions/AN group (p<0.05 for all), in terms of CK-19, HBME-1 ve NF-κB staining scores. Gal-3 staining scores were also found to be statistically