EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Urothelial cell carcinoma in renal transplant recipients has been rarely reported. Here, we report a case of high-grade papillary urothelial carcinoma in a renal transplant recipient who presented with hematuria. Sonographic evaluations (gray-scale ultrasonography, Doppler imaging, and strain sonoelastography) helped with diagnosis in our initial approach to the patient. Computed tomography was performed to confirm solid ureteral masses and staging of the disease. The patient, who underwent nephro-ureterectomy of the graft kidney, had that kidney for 6 years, 6 months. After surgery, the patient was symptom free and without evidence of recurrence or metastasis in 3 years of follow-up. Sonographic examinations have an important role in the evaluation of urothelial carcinoma of transplanted kidneys.

Key words : Kidney transplant, Malignancy, Nephroureterectomy, Sonographic scan, Urinary tract

Urothelial cell carcinoma, also called transitional cell carcinoma, is the most common primary malignancy of the urinary tract (renal pelvis, ureter, and bladder).¹ It is by far the most common in the urinary bladder, reflecting the larger surface area of the bladder mucosa. The ureter is the least common affected part of the urinary tract (1%), with the proximal third part of the ureter being the least commonly affected. Nevertheless, urothelial cell carcinoma accounts for over 90% of all cancers of the ureter.²

Kidney transplant recipients are more likely to develop neoplasms versus that shown in the general population as a result of their risk factors, including immunosuppression and the associated viral infections.3 After transplant, cancer (such as lip, skin, and anogenital), lymphoproliferative disorders, Kaposi sarcoma, and renal carcinoma may occur with increased incidence. The incidence of urinary tract cancers is also increased before renal replacement therapy, during dialysis, and after kidney transplant in patients with end-stage kidney disease.³

The transplanted kidney is normally placed in the extraperitoneal iliac fossa, most commonly the right. It can be visualized on that site easier than native kidneys via ultrasonography. Ultrasonography is commonly performed to evaluate possible post-operative complications. It is also the modality of choice for the diagnosis of urinary tract obstructions, with sensitivity of over 90%.⁴Vascular assessment can be performed via Doppler ultrasonography.⁵ Sonographic elastography can be utilized to evaluate the elasticity differences of parenchyma and/or mass. Computed tomography can be used to confirm solid ureteral masses and staging of the disease.⁶

There have been many reports about transitional cell carcinoma, but only a few cases of transitional cell carcinoma affecting the renal allograft have been published.⁷ Here, we present a rare case of urothelial carcinoma that developed in the collecting system of an allograft kidney.

A 30-year-old male patient who had received a deceased-donor kidney 6 years and 6 months earlier presented with hematuria. Serum creatinine level was high (9 mg/dL). Sonographic examinations and computed tomography were performed. The radiologist used a Logiq S7 Expert machine (GE Healthcare, Milwaukee, WI, USA) equipped with a C1-5-D convex probe for the gray-scale and Doppler ultrasonography and elastography examinations. The ultrasonography revealed urothelial mass, hydronephrosis, and a renal millimetric stone (not shown) (Figure 1A). A soft tissue area, which obliterated the ureteric lumen with clearly visualized blood flow inside the mass at power Doppler ultrasonography in the upper ureter, was also detected (Figure 1B). Strain-type elastography confirmed that the urothelial lesion was stiffer than renal parenchyma (Figure 2).

A percutaneous nephrostomy was placed into the collecting system, and the patient showed subsequent decreased creatinine level. Previous imaging findings were next confirmed by computed tomography, and soft tissue filling the upper ureteral lumen was observed (Figure 3). Biopsies of the papillary lesion were performed during antegrade ureteroscopy. Histopathologic results confirmed high-grade papillary urothelial carcinoma with focal lamina propria infiltration, and the patient underwent nephroureterectomy of the allograft.

Final pathologic examination revealed high-grade papillary urothelial carcinoma of the ureter and renal pelvis in the allograft kidney in 3 focuses. Millimetric renal cell carcinoma in the renal parenchyma was also noted, which could not be visualized by either ultrasonography or computed tomography. After surgery, the patient remained symptom free without evidence of recurrence or metastasis in 3 years of follow-up.

Immunosuppressive agents are routinely used after transplant. Studies have shown that immunosup-pressive regimens after renal transplant increase the risk of cancer.^3,8 The incidences of most commonly reported malignancies are higher in kidney trans-plant recipients than in the general population.8 The biological behavior of cancers in renal transplant patients is also more aggressive than similar cancers in nontransplant patients.⁹

Renal carcinomas make up 4.6% of posttransplant cancers versus 3% of cancers in the general population.¹⁰ For renal transplant recipients, renal cancer can develop both in the transplanted kidney and in the native kidney.¹¹ The incidence of urinary tract cancers is increased after kidney transplant.³ Urothelial cell carcinoma, also called transitional cell carcinoma, is the most common primary malignancy of the urothelium, accounting for more than 90% of tumors.¹ Squamous cell carcinoma, adenocarcinoma, and small cell carcinoma occur less frequently. The most common presenting symptom is painless hematuria.

Urothelial carcinoma can cause obstruction and dilatation in the collecting system. However, ultraso-nographic diagnosis is difficult when there is no dilatation and the tumor is small. Subramanyam and colleagues reported that transitional cell carcinomas of native kidneys can be discrete, solid masses causing separation of the central renal sinus echoes with similar echogenicity to renal parenchyma.¹² In a case report from Grant and associates, a less echogenic zone in the renal sinus than the normal sinus was shown.¹³ In another study, Vervloessem and associates reported a well-marginated polypoid mass, with moderate dilation in the collecting system seen in the renal pelvis. They also described clear vascularization in the mass, as shown by color Doppler ultrasonography.⁷

Color Doppler ultrasonography is useful for differentiation of other filling defects (such as blood clots or fungus balls) in the collecting system. Sonoelastography can be used to evaluate tissue elasticity, allowing variations in tissue hardness to be seen. The technique is based on the fact that malignant neoplasms have greater stiffness. A type of sonoelastography, the strain elastography, which we used in our case, can also provide relative information about hardness.¹⁴

With elastography, as shown in our case, in the color bar at the left side of the elastogram, red color reflects soft tissue, green color reflects medium stiff tissue, and blue color reflects more stiff tissue of the entire area undergoing qualitative elastography. The elastography score, which is obtained from the sonography machine and ranges from 0 (softest) to 6 (hardest), provides semiquantitative evaluation. Whereas a low elasticity score indicates soft tissue, a higher elasticity score indicates stiff tissue. In our case, the urothelial lesion had dominantly blue color reflecting hard tissue and had an elastography score of 3.3 and a ratio score of 2.6, reflecting a tissue stiffer than normal renal parenchyma. Computed tomo-graphy, as in our case, can be used to confirm the solid mass and to confirm staging of urothelial tumors in the renal pelvis.^6,7 The differential diagnosis of a soft tissue mass in the collecting system, however, can include other primary urinary tract malignancies, such as squamous cell carcinoma and metastatic tumors.¹⁵

The disease course of patients who have been diagnosed with urothelial carcinoma after renal transplant and immunosuppressive therapy is aggressive. A detailed evaluation of possible urothelial carcinoma is necessary when a renal transplant patient presents with hematuria. Ultrasonography is the main diagnostic tool to be used after the physical examination and laboratory evaluation of the patient.

Volume: 17 Issue: 2 April 2019

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