Surgical Pathology Criteria–

Gastrointestinal Tract Leiomyoma

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 Leiomyoma GIST (spindled, bland)
Usually arises in muscularis mucosae Nearly always arises in muscularis propria
Cytoplasm usually distinct, eosinophilic Cytoplasm frequently indistinct
CD117 negative CD117 74-95%
CD34 negative CD34 70%
DOG1 negative DOG1 87-94%
Desmin 100% Desmin 1-2% overall but 20% in esophagus
DOG1 is more sensitive for GIST than CD117 in side by side comparison

GI Mucosal Benign Epithelioid Nerve Sheath Tumor GI Leiomyoma (Epithelioid)
Most in lamina propria Most colonic lesions centered on muscularis mucosae
S100 positive S100 negative
Smooth muscle actin negative Smooth muscle actin positive
Restricted to colon Very rare in intestines
Most epithelioid leiomyomas reported in the past are now considered GIST

Schwannoma Leiomyoma
Frequent cell size variation Generally uniform cell size
Surrounded by lymphoid cuff No lymphoid cuff
S100 100% and GFAP 70-100% S100 and GFAP negative
Actin and desmin negative Actin and desmin positive

Inflammatory Fibroid Polyp Leiomyoma
Desmin negative Desmin positive
Spindled and stellate cells Spindled but no stellate cells
Abundant stromal eosinophils Eosinophils infrequent
Perivascular concentric cuffing common Lacks concentric cuffing
Fibrous or myxoid background May be myxoid but usually no fibrous background

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