Primary Mucinous Adenocarcinoma of Renal Pelvis- A Diagnostic Dilemma

Introduction: Primary mucinous adenocarcinoma of the renal pelvis is extremely rare, with only ~100 cases reported till now. Its pathophysiology is thought to comprise glandular metaplasia of the urothelium of the calyces and pelvis, as well as malignant transformation of the metaplasia. Unfortunately, there are no distinguishing symptoms or radiological characteristics.

Case Presentation: A 75-year-old man presented with pain in his left flank and intermittent fever. A physical examination showed swelling in left flank on inspection which was soft, non-tender, and ballotable with no local rise of temperature. The results of most laboratory tests were within normal limits. Plain radiography of the kidneys, ureter, and urinary bladder showed a large radio-opaque mass in the left kidney. Abdominal computed tomography showed left kidney measuring 24.8 x 12.4 cm with gross hydronephrosis with severe cortical thinning with large calculus of 2.7 X 3.1 x3.6cm in left pelviureteric junction. Diuretic- enhanced 99mTc DTPA renal scanning showed that the relative function of the left versus the right kidney was 11.19 versus 88.81 %. On the basis of the imaging findings, kidney dysfunction due to ureteropelvic junction stenosis with a large stone was initially diagnosed.

Although the cytopathology of gelatinous material was negative for malignancy, we could not rule out other disease, such as hidden malignancies of the kidney. As a result, we did a radical nephrectomy, and pathological investigation of the kidney revealed a mucinous adenocarcinoma in the renal pelvis. A bone scan and positron emission tomography revealed no additional malignancies, metastases, or remnant cancer.

Conclusions: Primary mucinous adenocarcinomas of the renal pelvis are extremely rare, and the majority are discovered by post-operative examination of resected specimens. Despite the difficulty of preoperative diagnosis, urologists should evaluate the possibility of primary mucinous adenocarcinoma in patients with severe hydronephrosis, renal stones, and chronic inflammation.