Bladder
Other tumors
Perivascular epithelioid cell tumor (PEComa)

Author: Turki Al-Hussain, M.D. (see Authors page)

Revised: 9 August 2016, last major update December 2014

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Bladder perivascular epithelioid cell tumor
Cite this page: Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bladderclearcellmyomelanocytic.html. Accessed December 10th, 2016.
Definition / General
  • Mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells that are immunoreactive for melanocytic markers
  • The PEComa family includes more common tumors such as angiomyolipoma (AML), clear-cell ("sugar") tumor of the lung and lymphangioleiomyoma, as well as less common tumors of the falciform ligament/ligamentum teres, bone, soft tissue and skin (Am J Surg Pathol 2009;33:304)
Terminology
  • Also called clear cell myomelanocytic tumor
Epidemiology
  • Rare; < 20 cases reported in bladder thru 2009
  • Median age 36 years (range, 19 to 48 years), 2 / 3 male
  • Not associated with tuberous sclerosis to date
Clinical Features
Prognostic Factors
    Proposed classification system for non-angiomyolipoma PEComas:
  • Benign: < 5 cm in size with low cellularity, low nuclear grade, mitotic rate less than 1 per 50 high power fields and no infiltration, necrosis or vascular invasion
  • Malignant: tumors that show 2 or more of the following features: size greater than 5 cm, infiltrative growth pattern, high mitotic rate, pleomorphism, necrosis or vascular invasion
  • Uncertain malignant potential: Only "malignant" feature is either nuclear pleomorphism / multinucleated giant cells or size > 5 cm (Am J Surg Pathol 2005;29:1558)
Case Reports
Treatment
  • Excision; possibly adjuvant therapy
Micro Description
  • Spindled and epithelioid cells with variable clear cell change
  • Delicate vasculature stroma
Micro Images

Images hosted on other servers:
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Epithelioid cells

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Various sites

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MelanA+

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Smooth muscle actin+; various stains at various sites


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Pleomorphic tumor cells

Positive Stains
Negative Stains
Molecular / Cytogenetics Description
  • Frequent deletion of 16p in which TSC2 gene is located
  • Also other gross chromosomal changes (Hum Pathol 2006;37:606)
Differential Diagnosis
  • Clear cell sarcoma of soft parts: collagenous and avascular stroma, frequently has tumor giant cells, S100+, actin-
  • Inflammatory myofibroblastic tumor: chronic inflammation, myxoid change, ALK1+ or ALK fusion
  • Leiomyosarcoma: diffuse cytoplasmic eosinophilia, perinuclear vacuoles, cigar shaped nuclei, prominent thick walled vessels, usually negative for melanocytic markers (but may be HMB45+)
  • Melanoma: usually melanotic, atypical melanocytes in adjacent mucosa, S100+, negative for muscle markers
  • Sarcomatoid carcinoma: in situ carcinoma present, keratin+, negative for melanocytic markers
  • Other smooth muscle tumors: fascicles, not packets of cells; more eosinophilic cytoplasm, HMB45-
  • GIST: no delicate vasculature stroma, HMB45-, CD34+, CD117+ (but PEComa can also be CD117+)