Abstract
IntroductionThe rare variant of renal epithelioid/pleomorphic angiomyolipoma has been reported in approximately 120 cases. One of the most important characteristics to differentiate these tumors from other renal cell neoplasms is their typical reactivity to premelanosome antigens. If such a tumor does not stain for HMB-45 or Melan-A, a specific diagnosis of epithelioid pleomorphic angiomyolipoma cannot be made with certainty.Case presentationWe present here what is, to the best of our knowledge, the first case of epithelioid/pleomorphic angiomyolipoma of the kidney in a 50-year-old Caucasian man with no history of tuberous sclerosis, and with a tumor marker profile negative for several premelanosome antigens. The tumor was composed of sheets of pleomorphic, round to polygonal epithelioid cells with prominent eosinophilic cytoplasm, large nuclei, many multinucleated, and very prominent nucleoli. There were prominent vessels and rare interspersed smooth muscle fibers, but adipocytes were not identified. A tumor marker profile showed tumor cell reactivity for CD68, calponin and focally for CD10. Intervening smooth muscle was reactive with smooth muscle actin. The tumor lacked reactivity for melanin-associated antigens HMB-45 and Melan-A, and for CD31, pan-cytokeratin (AE1/3) and desmin. Electron microscopic examination of tumor cells confirmed the presence of premelanosome-like granules.ConclusionsBased on the characteristic microscopic appearance of this tumor, and its overall tumor marker profile, we concluded this was a renal epithelioid/pleomorphic angiomyolipoma with a negative premelanosome antigen phenotype.
Highlights
The rare variant of renal epithelioid/pleomorphic angiomyolipoma has been reported in approximately 120 cases
In the approximately 120 reported cases of renal epithelioid variant of angiomyolipoma (EAML), the presence of premelanosome antigens (PMA) has been used as one of the main diagnostic landmarks [1,3]. This is in addition to the expression of some other important markers such as calponin and CD68, and the lack of expression of distinct epithelial cell markers such as cytokeratin AE1/AE3, high molecular weight cytokeratin and CAM5.2 [5]. If such a tumor does not stain for HMB-45 or Melan-A, a specific diagnosis of EAML cannot be made with certainty
While the paraffin sample used for this study provided suboptimal tissue fixation, we were able to identify tumor cells with finely granular organelles with a substructural periodicity resembling that of premelanosomes (Figure 2) [6]
Summary
Angiomyolipomas (AML) are members of a family of tumors derived from mesenchymal, perivascular epithelioid cells, normally clustered around blood vessels, and usually named PEComas (for ‘perivascular epithelioid cell tumors’). His symptoms continued and approximately two weeks later a chest, abdomen and pelvis computed tomography (CT) scan was performed This imaging study showed a solid heterogeneous mass (73×66×65mm) involving the parenchyma of the upper pole of the left kidney (Figure 1A). Sections of the mass showed round pleomorphic and occasionally multinucleated tumor cells with eosinophilic cytoplasm, macronucleoli, and rare mitotic figures; moderate interspersed smooth muscle fibers were observed, but adipocytes were not identified (Figure 1B).
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