What is the most prognostic factor for a patient with a gastric leiomyoma that has been excised?

Mitotic Figure is the Most Important Prognostic Factor for Gastric Leiomyoma

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

Ranking of Prognostic Factors

1. Mitotic Figure (Option B)

   • According to the European Society for Medical Oncology (ESMO) guidelines, mitotic count is the single most important prognostic indicator 1
   • High mitotic rates strongly correlate with aggressive behavior and poor outcomes regardless of other factors
   • Risk of metastasis varies dramatically based on mitotic rate:
     • Tumors >5cm with ≤5 mitoses/50 HPFs: 3.6% risk of metastasis
     • Tumors >5cm with >5 mitoses/50 HPFs: 55% risk of metastasis 1
   • Cox's proportional hazards regression analysis confirms ≥4 mitoses per 20 high-power fields as a significant unfavorable factor (hazard ratio 25.39) 2

2. Size (Option A)

   • While important, size has less impact than mitotic rate on prognosis 1
   • Becomes more significant when combined with high mitotic count
   • Tumors ≥6 cm have a hazard ratio of 5.57 in univariate analysis, but size was not significant in multivariate analysis 2

3. Vascular Invasion (Option C)

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

4. Node Invasion (Option D)

   • Least significant of the options presented
   • Lymph node metastasis is uncommon in gastric leiomyomas/GISTs 1
   • Not highlighted as a primary prognostic factor in the literature

Additional Important Prognostic Factors

• Tumor rupture: A highly unfavorable prognostic factor that can override other factors 1
• Nuclear atypia: Severe nuclear atypia is a significant unfavorable factor (hazard ratio 16.74) 2
• Presence of distant metastasis and/or direct invasion: Highest hazard ratio (36.60) in univariate analysis 2
• Mucosal ulceration: Associated with poor prognosis (hazard ratio 12.57), indicating high proliferative activity even in small tumors 2

Clinical Implications

• Follow-up intensity should be primarily determined by the mitotic rate, with more frequent surveillance for tumors with high mitotic activity 1
• Complete surgical excision with negative margins (R0) is the standard treatment for gastric leiomyomas 1
• Pathology reports should include three-dimensional tumor measurement, mitotic count per 5 mm², presence/absence of necrosis, and distance between lesion and margin 1
• Adjuvant therapy should be considered for high-risk patients, particularly those with high mitotic figures 1

The consistent finding across multiple studies is that mitotic count remains the most reliable and powerful prognostic indicator for gastric leiomyomas, even when controlling for other factors in multivariate analyses 1, 2, 3, 4.