Parenchymal mucinous cystadenoma of the kidney: a case report and literature review

Background Mucinous cystadenoma (MC) of the kidney is exceedingly rare. We found 22 similar cases in the literature. These masses are underdiagnosed due to radiologic similarities with simple renal cysts. Case presentation A 66-year-old man with a previous history of hypertension and anxiety was referred to our tertiary clinic with left flank pain. Ultrasound revealed a 60 mm-sized, complex cystic mass with irregular septa in the lower pole of the left kidney (different from last year's sonographic findings of a simple benign cyst with delicate septa). CT scan showed the same results plus calcification. Due to suspected renal cell carcinoma, a radical nephrectomy was performed. Postoperative histopathologic examination revealed a cyst lined by a single layer of columnar mucin-producing cells with small foci of pseudo-stratification, consistent with the MC's diagnosis. The first follow-up visit showed normal blood pressure without medication and no flank pain and anxiety after a month. Conclusion It is quite challenging to distinguish the primary MC of the kidney from a simple renal cyst based on clinical and imaging findings. The radiologic features of these entities overlap significantly. Thus, complex renal cyst and renal cysts with mural nodules should be followed closely to detect malignancy earlier.