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Gastrointestinal Tract Leiomyoma

Definition

  • Benign smooth muscle neoplasm arising in the gastrointestinal tract

Diagnostic Criteria

  • Fascicles of uniform spindle cells
  • Moderate to abundant eosinophilic cytoplasm
    • May contain eosinophilic globules
  • Elongate nuclei frequently blunt-ended
  • At most, focal cytologic atypia
    • Rare cases reported with large hyperchromatic “symplastic” nuclei
  • Mitotic rate ≤5/50 HPF appears to be the most important criterion
    • Most cases have no mitotic figures
    • Nearly all leiomyosarcomas have rates well above 5/50HPF
  • No coagulative tumor cell necrosis
  • Size is not a criterion for aggressive behavior
    • Range 0.1-18 cm
  • Leiomyomas vary in their incidence by site
    • They are more common than GIST in the esophagus
      • Most are intramural (involving muscularis propria)
      • Intramural tumors occur rarely at other GI sites
    • Muscularis mucosae leiomyomas are common in the rectum
      • They occur rarely at other sites
      • Essentially all smooth muscle tumors limited to the muscularis mucosae are benign
        • GIST are never limited to the muscularis mucosae
    • All leiomyomas are rare at other GI sites
  • CD117 and DOG1 negative
    • Any stromal neoplasm of the GI tract expressing CD117 or DOG1 should be considered a GIST

    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting/updates:12/5/09, 11/27/11

 

Supplemental studies

Immunohistology

Smooth muscle actin 100%
Desmin 100%
Vimentin 25%
CD117 0%
CD34 0%
S100 0%

Genetic Studies

  • All leiomyomas tested show no evidence of mutation in KIT

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

Clinical

  • Mean age about 60 except 37 in esophagus
  • Recurrence is very rare
    • Non-aggressive
    • No metastases

Bibliography

  • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010.
  • Miettinen M, Kopczynski J, Makhlouf HR, Sarlomo-Rikala M, Gyorffy H, Burke A, Sobin LH, Lasota J. Gastrointestinal stromal tumors, intramural leiomyomas, and leiomyosarcomas in the duodenum: a clinicopathologic, immunohistochemical, and molecular genetic study of 167 cases. Am J Surg Pathol. 2003 May;27(5):625-41.
  • Miettinen M, Furlong M, Sarlomo-Rikala M, Burke A, Sobin LH, Lasota J. Gastrointestinal stromal tumors, intramural leiomyomas, and leiomyosarcomas in the rectum and anus: a clinicopathologic, immunohistochemical, and molecular genetic study of 144 cases. Am J Surg Pathol. 2001 Sep;25(9):1121-33.
  • Miettinen M, Sarlomo-Rikala M, Sobin LH, Lasota J. Esophageal stromal tumors: a clinicopathologic, immunohistochemical, and molecular genetic study of 17 cases and comparison with esophageal leiomyomas and leiomyosarcomas. Am J Surg Pathol. 2000 Feb;24(2):211-22.
  • Miettinen M, Sarlomo-Rikala M, Sobin LH, Lasota J. Gastrointestinal stromal tumors and leiomyosarcomas in the colon: a clinicopathologic, immunohistochemical, and molecular genetic study of 44 cases. Am J Surg Pathol. 2000 Oct;24(10):1339-52.
  • Miettinen M, Sarlomo-Rikala M, Sobin LH. Mesenchymal tumors of muscularis mucosae of colon and rectum are benign leiomyomas that should be separated from gastrointestinal stromal tumors—a clinicopathologic and immunohistochemical study of eighty-eight cases. Mod Pathol. 2001 Oct;14(10):950-6.
  • Miettinen M, Sobin LH, Lasota J. True Smooth Muscle Tumors of the Small Intestine: A Clinicopathologic, Immunhistochemical, and Molecular Genetic Study of 25 Cases. Am J Surg Pathol. 2009 Mar;33(3):430-6.
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