Colon tumor
Mesenchymal tumors
Angiomyolipoma / PEComa

Author: Raul S. Gonzalez, M.D. (see Authors page)

Revised: 19 July 2016, last major update July 2016

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Angiomyolipoma [title] OR PEComa [title]

Cite this page: Angiomyolipoma / PEComa. website. Accessed October 24th, 2016.
Definition / General
  • Angiomyolipoma of colon: rare benign mesenchymal neoplasm, composed of vascular, adipocytic and smooth muscle elements, analogous to its more common counterpart in the kidney
  • PEComa: family of "perivascular epithelioid cell" neoplasms characterized by smooth muscle and melanocytic differentiation and positivity for HMB45; includes angiomyolipoma and PEComa-NOS
Essential Features
  • Angiomyolipoma: bland triphasic mesenchymal neoplasm in the PEComa family; most reported colonic cases have been HMB45 negative (if stained), casting some doubt on the diagnosis
  • PEComa: epithelioid neoplasm with atypia and HMB45 positivity; "PEComa-NOS" may be the most appropriate diagnosis for these lesions
  • Can arise anywhere in the gastrointestinal tract, though colon is most common
Clinical Features
  • Patients typically middle aged, with a slight female predominance; they very rarely have tuberous sclerosis
Prognostic Factors
  • Marked nuclear atypia, diffuse pleomorphism and high mitotic rate associated with risk of metastasis for PEComa (Am J Surg Pathol 2013;37:1769)
Case Reports
Micro Description
  • Angiomyolipoma: bland mural tumor composed of smooth muscle, blood vessel and mature adipose elements
  • PEComa: mural tumor composed of large spindled or epithelioid cells with nuclear atypia and eosinophilic cytoplasm
Micro Images

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PEComa: spindled and epithelioid lesion with marked atypia

Positive Stains
Negative Stains
  • Angiomyolipoma: HMB45 negative in nearly all reported examples (Am J Gastroenterol 1996;91:1852), unlike renal angiomyolipoma; this calls the diagnosis into doubt in such cases
Molecular / Cytogenetics Description
  • Tumors in the PEComa family are known to harbor TSC1, TSC2 and sometimes TFE3 mutations, though these have not specifically been demonstrated in the colon
Differential Diagnosis
  • Alveolar soft part sarcoma: epithelioid, eosinophilic cells arranged in a nested/alveolar pattern; nuclei are bland and are positive for TFE3; all reported colonic cases appear to be metastases
  • Neuromuscular and vascular hamartoma: bland injury related proliferation of smooth muscle, vessels and nerves/ganglia; native fat may be present; more common in small intestine