Renal cell carcinoma originating in the free wall of simple renal cyst: Two unusual case reports with literature review

Abstract

Rationale: Simple renal cyst (SRC) is a benign disease. However, rarely renal cell carcinoma (RCC) may be raised at the wall of a preexisting SRC. We herein describe 2 unusual cases of RCC arising from the outer surface of the free wall of the renal cyst.

Patient concerns: A 75-year-old female and a male were admitted to our department because of an asymptomatic renal cystic mass. Although the case history, preoperative imaging, and intraoperative examination of the cyst were carefully evaluated, no concerns were raised with respect to the underlying malignancy.

Diagnosis: RCC of the clear cell type was diagnosed based on the histology and pathological examination.

Interventions: With an initial diagnosis of SRC, the retroperitoneal laparoscopic de-roofing of the SRC was performed in both of the patients. When the diagnoses were confirmed 7 days postoperative, both of them were readmitted to our department for a radical nephroureterectomy.

Outcomes: The postoperative course was uneventful and the two patients did not undergo further chemotherapy. They are currently well and have no clinical or radiological signs of recurrence.

Lessons: Such cases remind us that seemingly benign renal cysts may harbor underlying neoplasia. Further evaluation and periodical follow-up are also recommended on the management of those seemingly benign renal cysts.

Figure 1

Abdominal plain CT scans of the first patient showing a 50 × 40-mm cyst in the middle pole of the right kidney, the density of the cyst contents was similar to that of water (A); IVP showing a mass arising from the middle pole of the right kidney, which does not distort the pelvis or calyces (B). CT = computer tomography, IVP = Intravenous pyelography.

Figure 2

Pathology of the first patient. (A) In biopsy specimen of the cyst wall, H&E staining shows clear cells with small nuclei forming alveolar or small nest structures; (B) imunohistochemical staining shows these cells are positive for cytokeratin; (C) H&E staining shows there are some giant cells but no clear tumor cells in the residual renal cyst all of nephrectomy specimen (all magnifications, ×200). H&E = hematoxylin and eosin.

Figure 3

Abdominal plain CT scans of the second patient showing a 78 × 51-mm cyst in the superior pole of the right kidney. An 8-mm mural nodule projecting from the outer surface of its free wall was then detected (A). Enhanced CT scans showing a renal cyst without septa, wall thickening or any enhanced solid component (B). CT = computer tomography.

Figure 4

Pathology of the second patient. (A) In biopsy specimen, H&E staining shows clear cells with small nuclei in the wall of the renal cyst; (B) imunohistochemical staining shows these cells are positive for cytokeratin; (C) H&E staining shows many clear tumor cells forming alveolar structures in the residual renal cyst all of nephrectomy specimen (all magnifications, ×200). H&E = hematoxylin and eosin.