What is the most prognostic factor for a patient with a gastric leiomyoma?

Mitotic Figure is the Most Important Prognostic Factor for Gastric Leiomyoma

The mitotic figure count is the most significant prognostic factor for gastric leiomyoma, with high mitotic rates strongly correlating with aggressive behavior and poor outcomes regardless of other factors. 1

Understanding Prognostic Factors in Gastric Leiomyoma

Gastric leiomyomas are benign smooth muscle tumors arising from the stomach wall. When evaluating prognosis after surgical excision, several factors must be considered, with varying degrees of importance:

Hierarchy of Prognostic Factors:

1. Mitotic Figure (Option B)

   • The mitotic index is consistently identified as the most powerful independent prognostic factor 2, 1
   • High mitotic rates dramatically increase risk of recurrence and metastasis regardless of other factors
   • According to ESMO guidelines, the difference in metastatic risk based on mitotic count is striking:
     • For 5-10 cm tumors: 3.6% risk with ≤5 mitoses/50 HPFs vs. 55% risk with >5 mitoses/50 HPFs 1
     • For >10 cm tumors: 12% risk with ≤5 mitoses/50 HPFs vs. 86% risk with >5 mitoses/50 HPFs 1

2. Tumor Size (Option A)

   • While important, size has less impact than mitotic rate 2, 1
   • A small tumor with high mitotic activity carries worse prognosis than a larger tumor with low mitotic activity
   • Size becomes more significant when combined with high mitotic count

3. Vascular Invasion (Option C)

   • Significant but secondary to mitotic count and size 1
   • Not identified as a primary prognostic factor in major guidelines 2

4. Node Invasion (Option D)

   • Least significant of the options presented
   • Lymph node metastasis is uncommon in gastric leiomyomas/GISTs 2, 1
   • Lymphadenectomy is generally not recommended during surgery due to low frequency of lymph node involvement 2

Additional Important Prognostic Considerations

• Tumor Location: Gastric leiomyomas generally have better prognosis than those in small bowel or rectum 2
• Tumor Rupture: Highly unfavorable prognostic factor that can override other factors 2
• Mucosal Ulceration: Associated with more aggressive histological features and poorer outcomes 3

Clinical Implications

For the presented case of a 9×7 cm gastric wall leiomyoma that was excised with safety margins:

1. The pathology report should specifically document the mitotic count per 5 mm² as this is the most critical prognostic indicator
2. Follow-up intensity should be primarily determined by the mitotic rate, with more frequent surveillance for tumors with high mitotic activity
3. Even with complete excision, high mitotic rates warrant closer monitoring due to increased risk of recurrence

Conclusion

While all four factors (size, mitotic figure, vascular invasion, and node invasion) contribute to prognosis, the evidence clearly establishes mitotic figure count as the single most important prognostic determinant for gastric leiomyoma, with tumor size as the second most important factor.