A patient is found to have elevated chromogranin A, synaptophysin-positive tumor cells, and a Ki-67 of 45%. According to current WHO 2022 classification, this neuroendocrine neoplasm would be graded as:
- A Large cell neuroendocrine carcinoma (NEC), high-grade
- B NET grade 3 (well-differentiated, high proliferation) ✓
- C NET grade 2
- D Mixed adenoneuroendocrine carcinoma (MANEC)
Correct answer: B. NET grade 3 (well-differentiated, high proliferation)
Explanation
WHO 2022 recognizes that well-differentiated neuroendocrine tumors (NETs) can occasionally have Ki-67 >20% (defining NET G3), a category distinct from poorly differentiated NECs such as large cell NEC or small cell NEC. The morphological differentiation (well vs. poorly differentiated) takes precedence over grade alone; NET G3 retains well-differentiated architecture unlike NEC. MANEC requires a dual adenocarcinoma and NEC component each exceeding 30%.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.