Undifferentiated pleomorphic sarcoma of the retroperitoneum mimicking a cortisol‐ and catecholamine‐secreting adrenal tumor

INTRODUCTION: Retroperitoneal tumors with endocrine abnormalities are suspected to be functional adrenal tumors. Retroperitoneal soft tissue sarcomas are rare tumors, without endocrine potential. CASE PRESENTATION: A 60‐year‐old male was referred for a 15 cm mass in the left suprarenal space. His plasma cortisol and catecholamine levels were elevated. He underwent open left adrenalectomy with radical nephrectomy and his endocrinological abnormalities were improved. Pathological findings suggested that it had originated from the retroperitoneal fat tissue, and a diagnosis of undifferentiated pleomorphic sarcoma was made based on the results of immunohistochemical analysis and fluorescence in situ hybridization. Interestingly, neither cortisol nor catecholamine was elevated when, 6 months after surgery, local recurrence developed. CONCLUSION: This is the first reported case of undifferentiated pleomorphic sarcoma accompanied by high levels of cortisol and catecholamine. We should keep in mind the possibility of tumors like retroperitoneal soft tissue sarcomas inducing endocrine abnormalities.