Perivascular epithelioid cell tumour

PEComa

Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. H&E stain.
Classification and external resources
eMedicine	orthoped/377
MeSH	D054973

In oncology, PEComa, also PEC tumour and perivascular epithelioid cell tumour, is a family of mesenchymal tumours consisting of peri vascular epithelioid cells (PECs).^[1] 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.^[2]

Establishing the malignant potential of these tumours remains challenging although criteria^[3] have been suggested; some PEComas display malignant features whereas others can cautiously be labeled as having 'uncertain malignant potential'.^[2] 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.^[2]

Many PEComa types shows a female predominance in the sex ratio.

Histologic appearance

PECs consist of perivascular epithelioid cells with a clear/granular cytoplasm and central round nucleus without prominent nucleoli.

Immunohistochemical markers

PECs typically stain for melanocytic markers (HMB-45, Melan A (Mart 1), Mitf) and myogenic markers (actin, myosin, calponin).

PECs and other conditions

PECs bear significant histologic 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^[2]
primary extrapulmonary sugar tumour^[2]

Thus, it has been advocated that the above could be classified PEComas.^[1]

Etiology

The precursor cell of PEComas is currently unknown; there is no normal counterpart "perivascular epitheloid cell".^[1] Genetically, PECs are linked to the tuberous sclerosis genes TSC1 and TSC2, 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 carcinomas, smooth muscle tumours, adipocytic tumours, clear cell sarcomas, melanomas and gastrointestinal stromal tumours (GIST).^[2]

References

1 2 3 Martignoni G, Pea M, Reghellin D, Zamboni G, Bonetti F (February 2008). "PEComas: the past, the present and the future". Virchows Arch. 452 (2): 119–32. doi:10.1007/s00428-007-0509-1. PMC 2234444. PMID 18080139.
1 2 3 4 5 6 Folpe, AL; Kwiatkowski DJ (2009). "Perivascular epitheloid cell neoplasms: pathology and pathogenesis". Human Pathology. 41 (1): 1–15. doi:10.1016/j.humpath.2009.05.011. PMID 19604538.
↑ Folpe AL, Mentzel T, Lehr HA, Fisher C, Balzer BL, Weiss SW (Dec 2005). "Perivascular epithelioid cell neoplasms of soft tissue and gynecologic origin: a clinicopathologic study of 26 cases and review of the literature". Am J Surg Pathol. 29 (12): 1558–75. doi:10.1097/01.pas.0000173232.22117.37. PMID 16327428.

Connective/soft tissue tumors and sarcomas (ICD-O 8800–9059) (C45–C49/D17–D21, 171/214–215)

Not otherwise specified

Connective tissue neoplasm

Fibromatous

Fibroma/fibrosarcoma:	Dermatofibrosarcoma protuberans Desmoplastic fibroma

Fibroma/fibromatosis:	Aggressive infantile fibromatosis Aponeurotic fibroma Collagenous fibroma Diffuse infantile fibromatosis Familial myxovascular fibromas Fibroma of tendon sheath Fibromatosis colli Infantile digital fibromatosis Juvenile hyaline fibromatosis Plantar fibromatosis Pleomorphic fibroma Oral submucous fibrosis

Histiocytoma/histiocytic sarcoma:	Benign fibrous histiocytoma Malignant fibrous histiocytoma Atypical fibroxanthoma Solitary fibrous tumor

Synovial-like

general:	Myoma/myosarcoma

smooth muscle:	Leiomyoma/leiomyosarcoma

skeletal muscle:	Rhabdomyoma/rhabdomyosarcoma: Embryonal rhabdomyosarcoma Sarcoma botryoides Alveolar rhabdomyosarcoma

Leiomyoma Angioleiomyoma Angiolipoleiomyoma Genital leiomyoma Leiomyosarcoma Multiple cutaneous and uterine leiomyomatosis syndrome Multiple cutaneous leiomyoma Neural fibrolipoma Solitary cutaneous leiomyoma STUMP

Complex mixed and stromal

Mesothelial

Vascular tissue neoplasm (ICD-O 9120–9179) (C49+C46/D18, 171+176/215)

Blood	Hemangiosarcoma Blue rubber bleb nevus syndrome Hemangioendothelioma Composite Endovascular papillary Epithelioid Kaposiform Infantile Retiform) Spindle cell Proliferating angioendotheliomatosis Hemangiopericytoma Venous lake Kaposi's sarcoma African cutaneous African lymphadenopathic AIDS-associated Classic Immunosuppression-associated Hemangioblastoma Hemangioma Capillary Cavernous Glomeruloid Microvenular Targeted hemosiderotic Angioma Cherry Seriginosum Spider Tufted Universal angiomatosis Angiokeratoma of Mibelli Angiolipoma Pyogenic granuloma

Lymphatic	Lymphangioma/lymphangiosarcoma Lymphangioma circumscriptum Acquired progressive lymphangioma PEComa Lymphangioleiomyomatosis Cystic hygroma Multifocal lymphangioendotheliomatosis Lymphangiomatosis

Either	Angioma/angiosarcoma Angiofibroma

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