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Dear Editor,

Cyst formation in native kidneys that occurs after the initiation of dialysis is called acquired cystic kidney disease (ACKD). Renal cell carcinoma (RCC) is known to be a complication of ACKD (1,2). Several studies have shown that RCC associated with ACKD of the native kidneys after renal transplantation has an incidence varying from 0.5% to 4.8%, and is often incidentally detected as an early tumor with a favorable prognosis (3) (Table 1).

Table 1.  Previous reports about renal cell carcinoma in the native kidney of a transplant recipient
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  1. Dialysis (time on dialysis). Transplantation (time after transplantation). Diagnosis (age at diagnosis). Incidence (incidence of renal cell carcinoma (RCC) in kidney tranpslant recipients (patients with RCC/ all patients). Mean ± standard deviation or range (minimum to maximum). BC, Basophilic papillary carcinoma; CCC, Clear cell carcinoma; CRC, Chromophobic renal cell carcinoma.

First authorDoubletKliemNeuzilletMoudouniSchwarzFilocamoKlatte
JournalJ UrolClin TransplantCancerBJU IntClin J Am Soc NephrolTransplant ProcBJU Int
Year reported1997199720052006200720092009
Dialysis (months)129 ± 49117.3 (43–206)No mention29 (12–60)50.6 ± 41.657.2 (8–120)115.2 (43.219.6)
Transplantation (months)90 ± 3575.8 (5–164)70.9 ± 49.4 (8–156)127, 574.4 ± 72.861.8 (12–156)567.2 (6–186)
Diagnosis (year)44 (15.2–86)50.2 (39.6–68.9)49.1 ± 9.9 31–63)45.8 (20–64)53.7 ± 13.150.3 (40 −58)58.1 (32.0–81.3)
Incidence of RCC5/129 (3.8%)12/2372 (0.5%)12/933 (1.2%)10/373 (2.6%)27/561 (4.8%)10/694 (1.4%)24/?
Tumor pathology (no.)Not reportedNot reportedCCC (7),BC (3),CRC (2)CCC (6), BC (4)CCC (16), BC (11)CCC (4), BC (6)CCC (13),BC (10), CRC (1)

A 60-year-old Japanese man was admitted to our hospital with fever of unknown origin and fatigue. HD had been started for chronic nephritis in 1984. Transplantation of a living-related donor kidney from his younger brother was done in May 2000, after which he received immunosuppression with drugs such as prednisolone, cyclosporine (50 mg daily), and mizoribine (100 mg daily). In May 2001, mizoribine was switched to mycophenolate mofetil (500 mg daily). On admission, his C-reactive protein level was 16.5 mg/dL. Blood culture was negative. Computed tomography (CT) revealed multiple nodular lesions that seemed to be metastatic tumors in both lungs (Fig. 1a). CT revealed multiple cystic lesions of both native kidneys, but a tumor was not detected even after intravenous contrast enhancement. Therefore, the patient's previous CT scans were reviewed. Most of the cysts that existed before renal transplantation (Fig. 1b) and that were consistent with ACKD showed a decrease of size in 2008 (Fig. 1c), but one cystic lesion with calcified walls in the left kidney showed asymmetrical enlargement from 1.5 cm to 4.0 cm in diameter during the 1-year period to 2009 (Fig. 1d). In April 2009, open left nephrectomy was performed. The resected specimen contained a whitish tumor with a maximum diameter of 3.0 × 5.0 cm adjacent to a large hemorrhagic cyst. Histologically, the tumor was clear cell carcinoma (Fig. 1e) with a fibrosarcoma-like component characterized by predominance of spindle cells (Fig. 1f). Accordingly, sarcomatoid renal carcinoma was diagnosed. The Tumor Node Metastasis (TNM) stage was T4, N2, M1, the Fuhrman nuclear grade was 3 or 4, and the pattern of infiltration was INF (infiltration)-β. There was prominent direct tumor invasion of the left renal vein, and enlarged para-aortic lymph nodes were also seen. After nephrectomy, the patient died of respiratory failure on 3 August 2009. Autopsy revealed that tumor emboli had reached the left inferior pulmonary artery via the inferior vena cava. In addition, there was lymphogenous metastasis to the mediastinal lymph nodes, and hematogenous metastases in the submucosa of the colon and the lungs.

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Figure 1. Computed tomography (CT) (a) reveals multiple nodular lesions consistent with tumor metastases in both lungs. (b) In 2000 (before renal transplantation), CT shows that the kidneys contain multiple cysts consistent with acquired cystic disease of the kidney (ACDK). (c) In 2008, the cysts in both kidneys have decreased in size. (d) In 2009, one cystic lesion of the left kidney has enlarged again. (e) The tumor was a clear cell carcinoma. (f) The tumor contained a fibrosarcoma-like component characterized by the predominance of spindle cells.

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Sarcomatoid carcinoma of the kidney is diagnosed when a sarcomatoid component is detected, regardless of the primary histology. Usually, the sarcomatoid component resembles malignant fibrous histiocytoma, fibrosarcoma, or undifferentiated spindle cell sarcoma. Patients with even a small focus of sarcomatoid carcinoma have a much worse prognosis than those whose tumors do not have any sarcomatoid foci (4). A literature search (PubMed) did not identify any previous reports about sarcomatoid carcinoma in the native kidney of a transplant recipient (Table 1).

In conclusion, we encountered a 60-year-old Japanese man who developed sarcomatoid carcinoma in his native left kidney after renal transplantation following long-term HD for 16 years. The disease was rapidly fatal. When renal transplantation is performed after chronic dialysis for over 10 years, the risk of sarcomatoid carcinoma should be considered. Long-term immunosuppression may play a key role in promoting the emergence of tumors in these patients.

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We thank Tatsuya Suwabe, Junichi Hoshino, Keiichi Sumida, Rikako Hiramatsu, Eiko Hasegawa, Masayuki Yamanouchi, Naoki Sawa, Michio Nakamura, Shinji Tomikawa, Kenmei Takaichi, Keihachiro Kuzuhara, and Yasunori Oota for their valuable advice regarding the therapeutic strategy. This study was funded by the Okinaka Memorial Institute for Medical Research.

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