Low Mitotic Activity in Papillary Thyroid Cancer: A Marker for Aggressive Features and Recurrence

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• The prognostic significance of low mitotic activity in papillary thyroid cancer (PTC) remains largely undefined.
• Understanding the behavior of PTC with varying mitotic rates is essential for effective patient management.

Purpose of the Study:

• To investigate the clinicopathologic features and recurrence patterns of PTC with low mitotic activity.
• To compare the behavior of PTC with low mitotic activity against PTC with no and high mitotic activity.

Main Methods:

• Retrospective review of 640 consecutive PTC cases (2018-2022).
• Mitotic activity classified as no, low (1-2/2 mm²), or high (≥3/2 mm²) per WHO criteria.
• Analysis included American Thyroid Association (ATA) risk stratification and Cox regression for recurrence.

Main Results:

• Low mitotic activity (17.2%) showed intermediate rates of vascular invasion, extrathyroidal extension, and lymph node metastasis.
• PTC with low mitotic activity had higher rates of intermediate/high ATA risk stratification and recurrence (15.5% vs. 4.5%).
• Low mitotic activity independently predicted recurrence (HR 2.96).

Conclusions:

• Low mitotic activity is a common finding in PTC, representing an intermediate behavior.
• It is associated with aggressive features and increased recurrence risk.
• Consideration of low mitotic activity is vital for accurate PTC risk stratification and recurrence prediction.