Zriedkavá forma perivaskulárneho epitelového tumoru (PEComu) v retroperitoneu
Rare Form of Perivascular Epithelial Tumor (PEComa) in Retroperitoneum

Summary/Abstract: Introduction: Lymphangiomyoma is a mesenchymal tumor with perivascular epithelioid cell differentiation and affects the lymph nodes. It belongs to the PEComa family. They are composed of histologically and immunohistochemically distinctive perivascular epithelioid cells that coexpresses melanocytic and muscle markers. The tumors can also be present in regions of falciform ligament, ligamentum teres, skin, uterus, and other viscera and soft tissue. In these regions they are rare, and are not associated with tuberous sclerosis. It occurs more often in women than in males, most often between 30 and 70 years of age. Usually are benign, but some cases have malignant behavior and simulate high grade sarcoma or other malignancy such as lymphoproliferative disease as it was in our case in the retroperitoneum by 31 year old woman. Methods: For a definitive histomorphologic examination we have got an operational material which has been fixed in formalin and standardly further processed. Tumour samples were fixed in 10 % buffered formalin and embedded in paraffin. Histological sections were studied after staining with hematoxylin and eosin (H&E) and 5 antibodies by methods of standard immunohistochemical techniques. Results: Histomorphologically, the tumour was composed of numerous vascular spaces, which were lined on the inner surface by endothelial cells and possessed outer proliferation of perivascular epithelioid cells. These perivascular cells had granular eosinophilic cytoplasm, nuclei without atypia, and expressed none to low mitotic activity. Vascular spaces were focally filled by lymphocytes and eosinophilic material. Focally, the remains of the lymphatic tissue were present as reminiscent of pre-existing lymph nodes. Immunohistochemically, endothelial cells in the inner side of vascular spaces exhibited positivity of hematopoietic progenitor cell antigen CD34, and perivascular epithelioid cells stained positively with alpha-smooth muscle actin, focally human melanoma black melanosomal glycoprotein (HMB45) and melanocytic antigen (MelanA/MART1). Proliferation activity assessed by Ki67 index was less than 1% positive cells. Conclusion: Particularly women in the reproductive age have to be considered regarding the disease. Sometimes it expresses itself only by chylous pleural exudation or chylous ascites, uncertain stomach pains without lung affliction. Lymphangiographical picture is a typical one. Immunohistochemically a positive reaction of perivascular ephitelial cells onto smooth muscle actin, HMB45, Melan A, is typical.

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