A 55-year-old woman undergoes thyroidectomy for a thyroid nodule. Histology shows papillary architecture with nuclear features: ground-glass (Orphan Annie eye) nuclei, nuclear grooves, pseudoinclusions, and overlapping nuclei. There is no capsular or vascular invasion. The tumor measures 0.8 cm. According to WHO 2022 endocrine classification, this is best classified as:

• A Papillary thyroid microcarcinoma (PTMC) — requires total thyroidectomy and RAI
• B Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)
• C Follicular thyroid carcinoma — requires molecular testing for TERT mutation
• D Papillary thyroid microcarcinoma (PTMC) — incidental low-risk tumor, active surveillance may be appropriate ✓

Explanation

A papillary thyroid carcinoma ≤1 cm is classified as papillary thyroid microcarcinoma (PTMC). For incidental, low-risk PTMC without high-risk features (no lymph node metastasis, no extrathyroidal extension, no aggressive variants, not adjacent to recurrent laryngeal nerve), active surveillance is now a recommended alternative to immediate surgery per American Thyroid Association and Japanese guidelines. NIFTP requires a fully encapsulated follicular-patterned tumor with papillary-like nuclei and no true papillae, capsular/vascular invasion. PTMC characteristically harbors BRAF V600E mutation (~60%).

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.