PEComa: what do we know so far?

Abstract

PEComas (tumours showing perivascular epithelioid cell differentiation) are a family of related mesenchymal neoplasms that include angiomyolipoma, lymphangiomyomatosis, clear cell "sugar" tumour of the lung, and a group of rare, morphologically and immunophenotypically similar lesions arising at a variety of visceral and soft tissue sites. These tumours all share a distinctive cell type, the perivascular epithelioid cell or "PEC' (which has no known normal tissue counterpart). PEComas show a marked female predominance and are composed of nests and sheets of usually epithelioid but occasionally spindled cells with clear to granular eosinophilic cytoplasm and a focal association with blood vessel walls. PEComas appear to arise most commonly at visceral (especially gastrointestinal and uterine), retroperitoneal, and abdominopelvic sites, with a subset occurring in somatic soft tissue and skin. Nearly all PEComas show immunoreactivity for both melanocytic (HMB-45 and/or melan-A) and smooth muscle (actin and/or desmin) markers. A subset of PEComas behave in a malignant fashion. This review examines the members of the PEComa family, with an emphasis on lesions arising outside of the kidney, lung and liver, and discusses preliminary evidence for pathological features that might predict malignant behaviour.

Activation of the mTOR pathway in sporadic angiomyolipomas and other perivascular epithelioid cell neoplasms

“…These lesions are defined as "mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells". While the origin of these cells is unknown, PEComas include angiomyolipoma (AML), lymphangio-leiomyomatosis (LAM), clear cell 'sugar' tumor of the lung, clear cell myomelanocytic tumor of the falciform ligament, and other "unusual clear cell tumors" designated as PEComas not otherwise specified (NOS) 2 . Such tumors may be conceptualized as monotypic epithelioid or spindled non-renal AML, akin to the monotypic tumors known to occur in TSC-associated renal AML.…”

Utility of [ 18 F]2-Fluoro-2-Deoxyglucose-PET in Sporadic and Tuberous Sclerosis-Associated Lymphangioleiomyomatosis

“…11,12 PEComas, including LAM, exhibit evidence of mTOR activation, including increased phosphorylation of S6. 13 Given the neoplastic nature of the LAM lesion, and the evidence for constitutive activation of the mTOR pathway that controls glucose homeostasis, we postulated that the LAM lesion would exhibit increased metabolic uptake of [ 18 F]2-fluoro-2-deoxyglucose (FDG) detected by PET scanning.…”

Perivascular Epithelioid Cell Tumors (PEComas) of the Head and Neck: Report of Three Cases and Review of the Literature

“…Based on the review by Hornick et al [6] PEComas (excluding renal AML, LAM, and CCST of lung) most commonly involve the retroperitoneal, visceral, abdominal, and pelvic sites. The gastrointestinal tract and the uterus are the most common extrarenal organs involved with soft tissue and skin being less frequently involved.…”

“…While the perivascular distribution of tumor cells is characteristic, it may not be seen in all PEComas, which most typically have a delicate vascular stroma surrounding tumor nests. Immunohistochemically, coexpression of melanocytic (HMB-45 and/or Melan-A) and myoid markers is characteristic [6]. The growing interest in PEComas has led to an increasing number of reports demonstrating different anatomic locations of these lesions, including several case reports involving various head and neck sites.…”