Malignant Perivascular Epithelioid Cell Tumor Mimicking Renal Cell Carcinoma: A Diagnostic Pitfall. (11th September 2019)

• Record Type: Journal Article
• Authors: Hakim, Natalya; Chornenkyy, Yevgen; Qasem, Shadi
• Is Part Of: American journal of clinical pathology. Volume 152(2019)Supplement 1
• Page Start: S62
• Page End: S62
• Publication Date: 2019-09-11
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqz113.061
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Introduction: Perivascular epithelioid cell tumors (PEComas) are defined by the World Health Organization (WHO) as mesenchymal tumors arising from perivascular epithelioid cells with myomelanocytic immunophenotype. In the kidney, they are often referred to as epithelioid angimyolipoma (AML). Most are benign but some can be malignant. Their rarity and wide differential render diagnosis challenging. Case Presentation: A 56-year-old male presented with a 3-month history of flank pain. Computed tomography (CT) identified bilateral necrotic heterogeneous enhancing kidney masses, with right significantly larger than left. Initially, the patient underwent a right radical nephrectomy. On gross examination, no tumor infiltration was observed. Histology demonstrated sheets of highly atypical cells with clear cytoplasm and easily identifiable nucleoli. Areas of spindle and rhabdoid differentiation were present. The initial diagnosis was renal clear cell (RCC) carcinoma, Fuhrman grade 4, with extensive rhabdoid and focal sarcomatoid features. A follow-up CT demonstrated a hypodense area within the right hepatic lobe. Status post liver resection and histomorphological examination, the lesion was identical to the renal mass except for focal areas of prominent epithelioid cells with eosinophilic cytoplasm. Immunohistochemical (IHC) stains of both masses were positive for Melan-A, HMB-45, and EMA but negative for PAX8, SOX10, S100, SMA, desmin, and cytokeratin. The initial diagnosis was amended to malignant AML with hepatic metastasis. Discussion and Conclusion: Renal PEComa (epithelioid AML) is a rare tumor with a prevalence of 0.44%. While most are benign, some are malignant with metastatic potential. The differential diagnosis for PEComa is broad and includes more common tumors like RCC, melanoma, clear cell sarcoma, and liposarcoma. The presence of spindle and epithelioid histology with eosinophilic cytoplasm in RCC should prompt additional IHC workup (HMB45, Melan-A, SMA, and EMA) in order to exclude PEComa/AML.