PEComa



PEComa


Elizabeth A. Montgomery, MD





Key Facts


Terminology



  • PEComa is abbreviation for neoplasms with perivascular epithelioid cell differentiation


  • Mesenchymal neoplasms composed of distinctive perivascular epithelioid cells



    • Includes angiomyolipoma (AML), clear cell “sugar” tumor of lung (CCST), lymphangioleiomyomatosis (LAM), clear cell myomelanocytic tumor of falciform ligament/ligamentum teres (CCMMT)


    • In many respects, PEComas are simply angiomyolipomas without fat


Etiology/Pathogenesis



  • AML, CCST, and LAM are associated with tuberous sclerosis but not other types


Clinical Issues



  • Most are benign


Microscopic Pathology



  • PECs consist of epithelioid to spindled cells arranged around vessels extending outward radially


  • Clear to granular, lightly eosinophilic cytoplasm and round to oval nuclei with small nucleoli


  • Myoid component with densely eosinophilic cytoplasm


  • Adipose tissue component present in lesions termed AML






Hematoxylin & eosin shows a PEComa with epithelioid cells proliferating around vessels. There are scattered large nuclei image in this field but no mitoses.






Hematoxylin & eosin shows a more myoid portion of a PEComa with more prominent cytoplasmic eosinophilia than in the previous image. This example also has scattered pleomorphic nuclei image.


TERMINOLOGY


Abbreviations



  • Perivascular epithelioid cell (PEC)


  • Thus neoplasms are termed “PEComa”


Synonyms



  • Extrapulmonary sugar tumor


  • Perivascular epithelioid cell tumor


  • Monotypic epithelioid angiomyolipoma


Definitions



  • Mesenchymal neoplasms composed of distinctive perivascular epithelioid cells (PEC) category includes



    • Angiomyolipoma (AML)


    • Clear cell “sugar” tumor of lung (CCST)


    • Lymphangioleiomyomatosis (LAM)


    • Clear cell myomelanocytic tumor of falciform ligament/ligamentum teres (CCMMT)


  • In many respects, PEComas are simply angiomyolipomas without fat


  • Subset displays overt histologic features of malignancy and malignant clinical behavior


ETIOLOGY/PATHOGENESIS


Association with Tuberous Sclerosis



  • Genetic alterations of tuberous sclerosis complex (TSC), losses of TSC1 (9q34) or TSC2 (16p13.3) genes


  • Autosomal dominant


  • Benign tumors of brain (most common), kidneys, heart, eyes, lungs, and skin



    • Name comes from characteristic tuber or potato-like nodules in brain, which calcify with age and become hard or sclerotic


  • AML, CCST, and LAM are associated with tuberous sclerosis but not other types


CLINICAL ISSUES


Epidemiology



  • Incidence



    • AML, CCST, LAM are rare



      • Other PEComas extremely rare


  • Age



    • CCMMT typically encountered in girls in late childhood


    • Most others seen in adults 50-60 years old


    • AML detected in younger patients in setting of tuberous sclerosis


  • Gender



    • Marked overall female predominance


Site



  • Reported in multiple sites



    • Kidney, liver, falciform ligament, deep soft tissues of extremities, skin, uterus, vulva, heart, gallbladder, gastrointestinal tract


Presentation



  • CCMMT presents as painful abdominal mass


  • Uterine examples manifest as uterine bleeding


  • Most other categories of PEComas present as painless masses


  • Brain tumors in patients with tuberous sclerosis present with seizures, developmental delay, behavioral problems


Treatment



  • Surgical excision


Prognosis



  • Most are benign



    • Rare documented examples of malignancy



      • Usually not in AML, LAM, or CCST types


      • Malignant examples behave as aggressive sarcomas


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Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on PEComa

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