Introduction: Cystic lesions in the renal pelvis may cause a diagnostic dilemma. These lesions may be benign or (pre)malignant and primary of secondary.
Case report: A 65-year-old woman presents with a complex cystic mass in the lower pole of the left kidney measuring approximately 16 cm in size and classified as Bosniak type 2F with minimally thickened septa and thick calcifications on non-contrast-enhanced computed tomography. The histopathological findings are consistent with a mucinous cystadenocarcinoma in the renal pelvis. Given the absence of a primary focus and based on clinical and radiological examination, the diagnosis of a primary renal neoplasm is preferred.
Discussion: A review of the literature is performed to evaluate the histological differential diagnosis and confirm the diagnosis. Epidemiology with an overview of available similar cases since 2009, as well as etiological factors, treatment and prognosis was reviewed.
Conclusion: Primary renal mucinous cystadenocarcinoma is an exceedingly rare tumor. Histopathology still remains the gold standard for the diagnosis of this tumor. Because of the rarity, secondary involvement from more common sites, such as ovary and gastrointestinal tract, should be thoroughly excluded.
Keywords: kidney; Mucinous cystadenocarcinoma; primary neoplasm; pseudomyxoma peritonei; renal pelvis.