BACKGROUNDThe perivascular epithelioid cell tumour (PEComa) family of tumours mainly includes renal and hepatic angiomyolipomas, pulmonary lymphangioleiomyomatosis and clear cell “sugar” tumour of the lung. Several uncommon tumours with similar morphological and immunophenotypical characteristics arising at a variety of sites (abdominal cavity, digestive tract, retroperitoneum, skin, soft tissue and bones) are also included in the PEComa family and are referred to as PEComas not otherwise specified.CASE SUMMARYWe present a 37-year-old female patient who underwent resection of an 8.5 cm × 8 cm × 4 cm retroperitoneal tumour, which eventually was diagnosed as PEComa of uncertain biological behaviour. Three years after the operation, the patient remains without any evidence of recurrence. A search was performed in the Medline and EMBASE databases for articles published between 1996 and 2018, and we identified 31 articles related to retroperitoneal and perinephric PEComas. We focused on sex, age, maximum dimension, histological and immunohistochemical characteristics of the tumour, follow-up and long-term outcome. Thirty-four retroperitoneal (including the present one) and ten perinephric PEComas were identified, carrying a malignant potential rate of 44% and 60%, respectively. Nearly half of the potentially malignant PEComas presented with or developed metastases during the course of the disease.CONCLUSIONRetroperitoneal PEComas are not as indolent as they are supposed to be. Radical surgical resection constitutes the treatment of choice for localized disease, while mammalian target of the rapamycin (mTOR) inhibitors constitute the most promising therapy for disseminated disease. The role of mTOR inhibitors as adjuvant or neoadjuvant therapies needs to be evaluated in the future.

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