Bladder
Other tumors
Perivascular epithelioid cell tumor (PEComa)



Topic Completed: 1 December 2014

Revised: 26 December 2018

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Bladder perivascular epithelioid cell tumor
Page views in 2018: 484
Page views in 2019 to date: 245
Cite this page: Al-Hussain T Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bladderclearcellmyomelanocytic.html. Accessed May 23rd, 2019.
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
Microscopic (histologic) description
  • Spindled and epithelioid cells with variable clear cell change
  • Delicate vasculature stroma
Microscopic (histologic) images

Images hosted on other servers:
Missing Image

Epithelioid cells

Missing Image

Various sites

Missing Image

MelanA+

Missing Image

Smooth muscle actin+; various stains at various sites


Missing Image

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+)
Back to top