Dia-gnostic Challenges and Extraordinary Treatment Response in Rare Malignant PEComa Tumor of the Kidney

Epithelioid angiomyolipoma (EAML) of the kidney, in contrast to classic benign renal angiomyolipoma, is a rare mesenchymal neoplasm with malignant potential. Represent-ing a member of the perivascular epithelioid cells (PEComa) tumor family aris-ing from the perivascular epithelioid cells, its accurate dia-gnosis and therapeutic approach remains challenging.

We report a case of a patient with malignant EAML, initially treated as renal cell carcinoma (RCC) at our institution. In this paper, we briefly summarize current status of clinical and histopathological knowledge of renal PEComas with metastatic potential and reconsider the dia-gnostic and therapeutic approach in this particular case to highlight the risk of mis-dia-g----nosis, malignant potential of renal PEComas and to demonstrate an unexpected treatment response.

The patient in our case was dia-gnosed with chromophobe RCC with sarcomatoid features. She underwent a radical nephrectomy and epinephrectomy with a satisfactory postoperative history. Local recurrence urged chemother-apy commencement with sunitinib in the first line, and shortly afterwards, the patient was enrolled in a clinical trial with everolimus, with an extraordinary favorable treatment response for 30 months. Follow-ing the extirpation of single abdominal nodularity after 36 months of treatment with mTOR inhibitor, and proceed-ing the everolimus administration, the dis-ease slowly progressed to the right liver lobe, result-ing in right hemihepatectomy in another 24 months. The immunoprofile of liver metastases with positive stain-ing of melanoma markers and smooth muscle markers induced the revaluation of the primary tumor and abdominal nodularity specimen to an invasive EAML of the kidney. Further dis-ease progression was unavoidable despite several chemother-apy regimens, and the patient died 104 months after primary dia-gnosis.

Renal tumors with adverse radiographic and histopathological features should become candidates for immunohistochemical stain-ing as its omission frequently leads to a misdia-gnosis, as showed in our case report. Atypical treatment response might suggest a possibility of a diagnostic mistake and should lead to reevaluation of the diagnostic and treatment process in the particular patient. Key words: renal PEComa -  epithelioid angiomyolipoma -  dia-gnosis -  everolimus.