Surgical Pathology Criteria

Gastrointestinal Tract Leiomyosarcoma

Differential Diagnosis

GI Leiomyoma GI Leiomyosarcoma
May be limited to muscularis mucosae Nearly always arises in muscularis propria
Atypia if present is focal Diffuse atypia
Mitotic rate ≤5/50HPF Mitotic rate >5/50HPF
No coagulative tumor cell necrosis May have coagulative tumor cell necrosis

GI Leiomyosarcoma GIST (spindled, cytologically malignant)
Frequently markedly pleomorphic Pleomorphism infrequent, even in malignant lesions
Frequently brightly eosinophilic cytoplasm Usually indistinct cytoplasm
CD117, DOG1 negative CD117 74-95%, DOG1 87-94%
Desmin variably positive Desmin 1-2%

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