PEComa
Encyclopedia
In oncology
, PEComa, also PEC tumour and perivascular epithelioid cell tumour, is a family of mesenchymal tumours consisting of perivascular
epithelioid cell
s (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.
cells with a clear/granular cytoplasm
and central round nucleus without prominent nucleoli.
, Melan A (Mart 1), Mitf) and myogenic markers (actin
, myosin
, calponin
).
Thus, it has been advocated that the above could be classified PEComas.
gene
s TSC1
and TSC2
, although this link is stronger for angiomyolipoma and lymphangioleiomyomatosis than for other members of the PEComa family.
s, smooth muscle tumours, adipocytic
tumours, clear cell sarcoma
s, melanoma
s and gastrointestinal stromal tumours (GIST).
Oncology
Oncology is a branch of medicine that deals with cancer...
, PEComa, also PEC tumour and perivascular epithelioid cell tumour, is a family of mesenchymal tumours consisting of perivascular
Vascular
Vascular in zoology and medicine means "related to blood vessels", which are part of the circulatory system. An organ or tissue that is vascularized is heavily endowed with blood vessels and thus richly supplied with blood....
epithelioid cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s (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
Angiomyolipoma
Angiomyolipoma are the most common benign tumour of the kidney and are composed of blood vessels, smooth muscle cells and fat cells. Angiomyolipoma are strongly associated with the genetic disease tuberous sclerosis, in which most individuals will have several angiomyolipoma affecting both kidneys...
and pulmonary lymphangioleiomyomatosis
Lymphangioleiomyomatosis
Lymphangioleiomyomatosis is a rare lung disease that results in a proliferation of disorderly smooth muscle growth throughout the lungs, in the bronchioles, alveolar septa, perivascular spaces, and lymphatics, resulting in the obstruction of small airways and lymphatics...
, 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.
Histologic appearance
PECs consist of perivascular epithelioidEpithelioid
An epithelioid cell is a cell that resembles epithelial cells in that it directly contacts its neighboring cells via cell surface molecules or junctions. Unlike epithelial cells, however, epithelioid cells make contacts over their entire surface, rather than at restricted portions. The term...
cells with a clear/granular cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
and central round nucleus without prominent nucleoli.
Immunohistochemical markers
PECs typically stain for melanocytic markers (HMB-45HMB-45
HMB-45 is a monoclonal antibody that reacts against an antigen present in melanocytic tumors such as melanomas. It is used in anatomic pathology as a marker for such tumors....
, Melan A (Mart 1), Mitf) and myogenic markers (actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
, myosin
Myosin
Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
, calponin
Calponin
Calponin is a calcium binding protein. Calponin tonically inhibits the ATPase activity of myosin in smooth muscle. Phosphorylation of calponin by a protein kinase, which is dependent upon calcium binding to calmodulin, releases the calponin's inhibition of the smooth muscle ATPase.- Sturcture and...
).
PECs and other conditions
PECs bear significant histologic and immunohistochemical similarity to:- angiomyolipomaAngiomyolipomaAngiomyolipoma are the most common benign tumour of the kidney and are composed of blood vessels, smooth muscle cells and fat cells. Angiomyolipoma are strongly associated with the genetic disease tuberous sclerosis, in which most individuals will have several angiomyolipoma affecting both kidneys...
, - clear-cell sugar tumour (CCST),
- lymphangioleiomyomatosisLymphangioleiomyomatosisLymphangioleiomyomatosis is a rare lung disease that results in a proliferation of disorderly smooth muscle growth throughout the lungs, in the bronchioles, alveolar septa, perivascular spaces, and lymphatics, resulting in the obstruction of small airways and lymphatics...
, and, - clear-cell myomelanocytic tumour of ligamentum teres/falciform ligamentFalciform ligamentThe falciform ligament is a ligament that attaches the liver to the anterior body wall.It is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed downward and backward and its apex upward and backward...
. - abdominopelvic sarcoma of perivascular epitheloid cells
- primary extrapulmonary sugar tumour
Thus, it has been advocated that the above could be classified PEComas.
Etiology
The precursor cell of PEComas is currently unknown; there is no normal counterpart "perivascular epitheloid cell". Genetically, PECs are linked to the tuberous sclerosisTuberous sclerosis
Tuberous sclerosis or tuberous sclerosis complex is a rare multi-system genetic disease that causes non-malignant tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioral...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s TSC1
TSC1
Tuberous sclerosis protein 1, also known as TSC1 or hamartin, is a human protein and gene.- Function :This peripheral membrane protein was implicated as a tumor suppressor...
and TSC2
TSC2
Tuberous sclerosis protein 2, also known as TSC2 and Tuberin, is a human protein and gene.-Interactions:TSC2 has been shown to interact with FOXO1, GSK3B, Peptidylglycine alpha-amidating monooxygenase, RAP1A, MAPK1, AKT1, AXIN1, TSC1, PTK2, Protein kinase, AMP-activated, alpha 1, YWHAZ, RPS6KA1,...
, although this link is stronger for angiomyolipoma and lymphangioleiomyomatosis than for other members of the PEComa family.
Differential diagnosis
PEComas are rare and can have myriad features; therefore, they can be confused with carcinomaCarcinoma
Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during...
s, smooth muscle tumours, adipocytic
Adipocyte
However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...
tumours, clear cell sarcoma
Sarcoma
A sarcoma is a cancer that arises from transformed cells in one of a number of tissues that develop from embryonic mesoderm. Thus, sarcomas include tumors of bone, cartilage, fat, muscle, vascular, and hematopoietic tissues...
s, melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
s and gastrointestinal stromal tumours (GIST).