Case details: A some around 35-year-old female presented with a thyroid mass.
Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)
Histopathology:
– Cellular thyroid tumor with an intact capsule, and compact follicular growth pattern.
– Partial/weak nuclear features of papillary thyroid carcinoma are seen: Nuclear chromatin clearing, enlargement, crowding/overlapping, irregular nuclear border, and few have intranuclear grooves (yellow arrow).
– Intranucelar inclusions are not seen.
– NO evidence of papillary architecture, psammoma bodies, solid/trabecular or solid growth pattern, infiltrative border, vascular invasion, necrosis or mitoses.
Practical points of Pathoclinics:
- In previous years, NIFTP are diagnosed as a follicular variant of papillary thyroid carcinoma FVPTC, non-invasive encapsulated type on histology ground. The main purpose of renaming is avoid the term “carcinoma” and replace it with NIFTP, to prevent extensive radical surgery due to its excellent long-term biological behavior.
- In my opinion, the prevalence of NIFTP is more than papillary thyroid carcinoma. The possibility of subjectivity in a diagnosis of NIFTP is more, because of the presence of a variable degree of nuclear features of papillary thyroid carcinoma.
- On cytology (FNAC), many cases were previously designated as a follicular variant of papillary thyroid carcinoma, considering the presence of nuclear features of PTC. So consequently, such cases were treated with radical surgery and the patient has to take lifelong thyroxin treatment. Most of such cases had an intact capsule (which is not able to pick up on cytology) on follow-up histology and very indolent behavior. In TBSRTC, NIFTP has extensive room to go in any category like suspicious for follicular neoplasm, suspicious for papillary thyroid carcinoma or atypia of unknown significance. In presence of repetitive follicular patterns on thyroid cytology smears along with nuclear features of PTC (mostly without intranuclear inclusions), the possibility of NIFTP should be raised in the report. Here there is a need for the thyroid frozen section and intra-operative cytology in doubtful cases.
- Complete evaluation of the capsule is MUST, to designate the tumor as a NIFTP. In NIFTP, the capsule can be thick or thin but must be INTACT. Follicular structures are micro or macro-follicular types with the presence of a variable amount of colloid.
- NIFTP has uncommon to have frequent intranuclear inclusions and does not show the papillary architecture (not more than 1% of total tumor area). The presence of more than one papilla and more than occasional intranuclear inclusions should alert the pathologist to search for other areas to rule out conventional Papillary thyroid carcinoma.
- Lobectomy or partial thyroidectomy is adequate management for NIFTP.
- NIFTP has a RAS mutation, which is common with follicular thyroid neoplasm and not in line with papillary thyroid carcinoma. BRAFV600E and TERT promoter mutations are not seen in NIFTP.
- Extremely rarely NIFTP develop metastasis.
