Perivascular epithelioid cell tumour, also known as PEComa or PEC tumour, is a family of

mesenchymal tumour Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...

s consisting of perivascular epithelioid cells (PECs). These are rare tumours that can occur in any part of the human body. The cell type from which these tumours originate remains unknown. Normally, no perivascular epitheloid cells exist; the name refers to the characteristics of the tumour when examined under the microscope. Establishing the malignant potential of these tumours remains challenging although criteria have been suggested; some PEComas display malignant features whereas others can cautiously be labeled as having 'uncertain malignant potential'. The most common tumours in the PEComa family are renal angiomyolipoma and pulmonary lymphangioleiomyomatosis, both of which are more common in patients with tuberous sclerosis complex. The genes responsible for this multi-system genetic disease have also been implicated in other PEComas. Many PEComa types shows a female predominance in the sex ratio.

Cause

The precursor cell of PEComas is currently unknown; there is no normal counterpart "perivascular epitheloid cell". Genetically, PECs are linked to the

tuberous sclerosis Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that causes non-cancerous tumours to grow in the brain and on other vital organs such as the kidneys, heart, liver, eyes, lungs and skin. A combination ...

genes TSC1 and TSC2, although this link is stronger for angiomyolipoma and lymphangioleiomyomatosis than for other members of the PEComa family.

Diagnosis

Histology

PECs consist of perivascular

epithelioid Epithelioid may refer to: * Epithelioid cell, a cell that resembles epithelial cells * Epithelioid sarcoma, a soft tissue tumour * Epithelioid hemangioendothelioma, a vascular tumour occurring in the lining of blood vessels * Epithelioid blue nevus ...

cells with a clear/granular cytoplasm and central round nucleus without prominent

nucleoli The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sig ...

Immunohistochemical markers

PECs typically stain for melanocytic markers ( HMB-45, Melan A (Mart 1),

Mitf Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the ''MITF'' gene. MITF is a basic helix-loop-helix leucine zipper transcription factor ...

) and myogenic markers ( actin,

myosin Myosins () are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The first myosin ...

, calponin).

Differential diagnosis

PECs bear significant

histologic Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

and immunohistochemical similarity to: * angiomyolipoma, *clear-cell sugar tumour (CCST), * lymphangioleiomyomatosis, and, *clear-cell myomelanocytic tumour of ligamentum teres/ falciform ligament. *abdominopelvic sarcoma of perivascular epitheloid cells *primary extrapulmonary sugar tumour Thus, it has been advocated that the above could be classified PEComas. PEComas are rare and can have myriad features; therefore, they can be confused with

carcinoma Carcinoma is a malignancy that develops from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesodermal ...

smooth muscle tumour Smooth muscle tumours show a smooth muscle differentiation. There are two main types of smooth muscle tumour: the benign leiomyoma and the malignant leiomyosarcoma Leiomyosarcoma is a malignant (cancerous) smooth muscle tumor. A benign tumor orig ...

s, adipocytic tumours, clear cell sarcomas,

melanoma Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye ( ...

s and

gastrointestinal stromal tumour Gastrointestinal stromal tumors (GISTs) are the most common mesenchyme, mesenchymal neoplasms of the Human gastrointestinal tract, gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. Th ...

s (GIST).

References

External links

{{Vascular tumors Vascular neoplasia