Pecom D18.01

Crowson, 2003

Cutaneous PEComa is a very rare (< 40 cases have been described so far) mesenchymal tumor entity whose dominant cell type is the "perivascular epithelioid cell", or PEC. This cell type has defined histological characteristics:

• epithelioid form
• clear to pale eosinophilic cytoplasm
• perivascular arrangement
• co-expression of smooth muscle actin/desmin with melanocytic markers (Melan A, HMB45, MiTF).

Systemic PECom can occur at any age. Both sexes are affected. They can occur in any localization. The gastrointestinal tract is one of the most common anatomical sites of origin, accounting for 20-25% of all reported cases of perivascular epithelioid cell tumors without further specification (PEComas-NOS) (Chen Z et al. 2016). Furthermore, the pancreas and lungs are affected (Jiang H et al. 2016). Complications of organ manifestation may include hemodynamically relevant hemorrhage.

Preferably occurring in women between 30-50 years.

Especially lower leg

Clinically it is a random finding. Non-characteristic brown, painless, firm nodules up to 1.0 cm in size are described as "histiocytoma-like".

The diagnosis of PECom is made histologically, as the clinical features of the tumour are not very concise. The diagnosis is a dermal clear cell tumour separated from the unaltered surface epithelium by a border zone, which is only weakly stained in the HE preparation. The tumour cells are diffusely arranged epithelioid tumour cells with a round chromatid dense cell nucleus and a bright, slightly eosinophilic cytoplasm. At higher magnification, fine CD31 positive capillary structures are found which are surrounded by the epiheloid cells in a nest-like manner. The tunmor cells are characterized by a pronounced reactivity of the cells towards HMB45, with neg. S100 and often neg. melan A. Positive myoid markers can be actin, myosin and calponin.

Cutaneous PEComes represent about 8% of all PEComes. In contrast to visceral PEComas, they are predominantly classified as benign (of 36 cases described, 1 metastasis occurred once).

Visceral PEComas can occur in combination with the tuberous sclerosis complex.

1. Charli-Joseph Y et al (2014) Primary cutaneous perivascular epithelioid cell tumor: a clinicopathological and molecular reappraisal. J Am Acad Dermatol 71:1127-1136
2. Chen Z et al (2016) A systematic review: perivascular epithelioid cell tumor of gastrointestinal tract. Medicine (Baltimore) 95:e3890.
3. Crowson AN et al (2003) Cutaneous clear cell myomelanocytic tumor-perivascular epithelioid cell tumor: firsgt reported case. Mode Pathol 16: 400
4. Greveling K et al (2013) Malignant perivascular epithelioid cell tumor: a case report of a cutaneous tumor on the cheek of a male patient. J Am Acad Dermatol 69:e 262-264
5. Jiang H et al (2016) Pancreatic perivascular epithelioid cell tumor: A case report with clinicopathological features and a literature review. World J Gastroenterol 22(:3693-3700.
6. Kneitz H et al (2015) Cutaneous PEComa of the right lower leg. JDDG 13: 815-817
7. Ieremia E et al (2014) PEComa: a rare entity to consider in an unusual site. Am J Dermatopathol 36:e198-201
8. Peterson I (2013) The new WHO classification and current results in soft tissue tumor pathology. The Pathologist 34: 436-448.
9. Pusiol T et al (2012) HMB-45 negative clear cell perivascular epithelioid cell tumor of the skin. Acta Dermatovenerol Croat 20: 27-29.
10. Shim HS et al.(2014) Cutaneous angiomyolipoma in the forehead. J Craniofac Surg 25:1120-1122
11. Wu J et al (2014) Cutaneous metastasis of a perivascular epithelioid cell tumor. Cutis 93: E 20-21