Malignant perivascular epithelioid cell tumor of the ureter:A case report and literature review
This study reports a rare case of malignant perivascular epithelioid cell tumor(PEComa)of the ureter.A patient presented with persistent right-sided lower back discomfort for 15 years with worsening symptoms and was found to have a lesion in the right ureter.Abdominal computed tomography and magnetic resonance imaging revealed a mass in the junction of the middle and upper sections of the right ureter,accompanied by severe hydronephrosis in the upstream ureter and renal pelvis.Urinary exfoliative cytology revealed malignant tumor cells.Ureteroscopy localized the tumor of the upper section of the right ureter,measuring approximately 1.5 cm in maximum diameter,with no polypoid growth observed in the surrounding mucosa and no lesions in the bladder.Biopsy findings confirmed a neoplastic lesion in the right ureter,but limited tissue volume and immunohistochemical results ruled out an epithelial origin,necessitating further differentiation between PEComa and alveolar soft part sarcoma.To clarify the diagnosis,the patient underwent laparoscopic partial ureterectomy.Postoperative pathological diagnosis confirmed malignant PEComa with tumor invasion into the outer layer and venous involvement.Malignant PEComa of the ureter is rare,and diagnostic criteria include tumor size>5 cm,infiltrative margins,highly differentiated and cellular nuclei,mitotic figures≥1/50 HPF,tumor necrosis,and vascular invasion.Malignancy is considered when two or more criteria are met.Tumor size may depend on the available growth space at the site of origin and may not be a definitive criterion for malignancy.When biopsy samples are limited and pathological is atypical,cytological examination and immunohistochemistry are critical for differentiation and diagnosis.While transcription factor enhancer 3(TFE3)immunohistochemical positivity can assist in diagnosing specific tumors,its sensitivity and specificity are limited.It cannot solely confirm a diagnosis or replace molecular testing for gene rearrangement.In cases with atypical pathological features,comprehensive analysis of immunohistochemical results and morphological findings,supplemented by molecular testing when necessary,is essential for accurate diagnosis.
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