NIFTP & Implications for Thyroid FNA Cytology
The histopathological diagnosis of NIFTP, a newly described thyroid tumor will have significant implications for thyroid FNA cytology.
These implications were pointed out in an article from the Brigham and Women’s Hospital by Kyle Strickland & colleagues showing that if NIFTP tumours are excluded from a ‘malignant’ cytological category the risk of malignancy for Bethesda Class VI (malignant) FNA’s will reduce to 93.6%, for class V (suspicious) to 45.7% for Class IV to 37.5%, for class III to 21.6% and for benign (class II) to 21.6%.
A similar multi-institutional series by Faquin et al. showed similar findings with a risk of malignancy of 95.7% for Bethesda Class VI FNA’s, 59.2% for class V FNA’s, 18.0 % for Class IV FNAs, 17.6% for Class III & 5.8% for Class II thyroid FNA’s. Another article covering aspects of thyroid FNA cytology in relation to NIFTP is by Maletta et al.
If NIFTP tumour lesions are no longer regarded as ‘carcinomas’ because the cytological features of NIFTP lesions overlap with classical type papillary carcinoma & follicular variants of papillary carcinoma which do have foci of capsular or vascular invasion & which are therefore not classified as NIFTP tumors this new tumor diagnostic entity is clearly is going to present some interesting & slightly challenging transitional issues for clinicians, pathologists & cytologists working within multidisciplinary clinical teams.
Strickland KC et al. Thyroid 2015;25:1-6
Faquin WC et al. Cancer Cytopathology 2016;124:181-7
Maletta et al Hum Pathol. 2016 Apr 13. pii:S0046-8177(16)30033-8. doi: 10.1016/j.humpath.2016.03.014.